Download Question Bank Physics Class 12

Question Bank Unit I: ELECTROSTATICS. (1 MARKS)
1 . How many electrons must be removed form a conductor so that it acquires a charge of 3.5 nC.
2. Define electric dipole moment and write its S.I. Unit.
3. Name the physical quantitiy whose SI unit is Joule/Coulomb. Is it a scalar or vector quantity?
4. What is the the value of electrostatic potential on Equatorial line of equipotential surface?
5. Define dielectric constant of a medium in terms of electrostatics force.
6. Define electric flux and write it’s S.I. unit.
7. What is the net electric flux when an electric dipole is enclosed by a closed surface.
8. A charge q micro coulomb is placed at the center of the cube. What is the electric flux through one face.
How much work is done in moving the 500 micro coulomb charge on an equipotential surface.
9. Why is the electric potential energy of a pair of like point charges positive?
10. A charge q0 has been taken from R to A, R to B and R to C. In which condition work done is maximum?
11. Does an electric charge experience a force due to the field, it produces it self?
12. Two capacitors C1 = 3μF and C2 = 6μF are connected in series and charged by connecting a battery of
voltage V= 10volt in series with them. They are then disconnected from the battery and loose wires are
connected together. What is the final charge on each?
Short Answer questions (2 marks)
1. Draw the electric field lines due to a uniformally charged this spherical shell when the charge on the shell
is (i) Positive (ii) Negative
2. What is equipotential surface so that electric field is always directed perpendicular to equipotential
surface ?
3.
A parallel plate capacitor with air between the plates has a capacitance of 8 micro Farad, the separation
between the plates is now reduced by half and the space between them is filled with a medium of dielectric constant
Calculate the value of the capacitance of the capacitor in the second case.
4. Two electrons have been removed from each atom. Find the distance between two such atoms, if they
repel each other with a force of 8.8 X 10-9 N, when placed in free space.
5. It two point charges q1 and q2 are 3m apart and their combined charge is 20μC. If one repels the other
with a force of 0.075 N, What are the two charges?
6. Two charges 3 X 10-8 C and -2 X 10-8 C are located 15 cm apart. At what point on the line joining the two
charges is the electrical potential to be zero.
7. The effective capacitance of two capacitors is 3μF, when they are connected in series and parallel
respectively, Compute the capacitance of each capacitor.
8. If a charge +Q is revolved once round another charge +q in a circle of radius R how much work is done?
9. The electric potential at 0.9m from a point charge is +50v. Find the magnitude and nature of charge.
10. In the electric field shown, the electric field lines on the left have twice the separation as that between
those on the right. If the magnitude of the field at point A is 40NC-1. Calculate the force experienced by a
proton placed at point A. Also find the magnitude of electric filed at the point B.
11. The flux of the electric field, through the closed surface S’ is found to be four times that through the
closed spherical surface S. Find the magnitude of the charge Q. Given q1 = 1μC, q2 = - 2μC, and q3 =
9.854μC. [Ans: 26.562 μC]
1.
2.
Short Answer questions (3 marks)
State Gauss’ theorem. Derive an expression for electric field due to uniformally charged straight wire of linear
charged density lambda.
State the working principle of Van- de- Graff Generator.
3. Two charges } 10μC are placed 5.0mm apart. Determine the electric field at (a) a point on the axis of the
dipole 15 cm away from its centre – O on the side of the positive charge, (b) a point 15 cm away from
point – O on a line passing through ‘O’ and normal to the axis of the dipole. [(a) 2.6 X 105 NC-1 (b) 1.33 X
105 NC-1 ]
4. A parallel plate capacitor is charged by a battery which is the disconnected , a dielectric slab then
inserted in between the plates. Explain what changes if any will takes place in (i)
Capacitance
(ii)
Electric field between the plates (iii) Energy stored in the capacitor
Justify your answer in each case.
5. An electric dipole AB consists of charges } 5 nC and separated by a distance of 2 X 10-3 m as shown in fig.
The Dipole is placed near a long line charge having linear charge density 4.5 X 10-4 cm-1, such that the -ve
charge is at a distance A = 2.5 cm from the +ve charge. Find the force acting on the dipole. [Ans:0.12 N
towards the line of charges].
6.
Find the effective capacitance between the terminals X and Y of the network shown. Given that C1 = 5 μF,
C2 = 10 μF, C3 = 2 μF, C4 = 4 μF and C5 = 10 μF.
7.
Suppose that the earth has a net charge that is not zero. Is it still possible to adopt the crash as a
structural reference point of potential and assign the potential V=0 to it?
8.
The electric field due to a point charge depends on the distance r as (1/r2), similarly indicate how each of
the following quantities depends on it?
a. Intensity of light from a point source.
b. Electric potential due to a point charge and
c. Electric potential at a distance r from the centre of a charged metallic sphere of radius (r < R).
Long Answer questions (5 marks)
State principle of working of capacitor, derive an expression for capacitance of parallel plate capacitor with
air between the plates, also derive an expression for energy stored between the plate.
2.
Define electric field and derive an expression for electric field due to and electric dipole at point lying on
(i) Axial line
(ii) Equatorial line
3. (a.) Derive an expression for capacitance of a parallel plate capacitor of thickness t (t<d) is inserted
between the plates of capacitor.
(b) Net capacitance of three identical capacitor in 2 micro farad. What will be there net capacitance when
they connected in parallel. Also find the ratio of energy stored in two configuration if they are both
connected to the same source?
4. (a) Show that there is no translatory force act on an electric dipole placed in uniform electric field, Also
derive an expression for torque acting experienced by it.
(b) Two charges 5 nano coulomb and -2 nano coulomb are placed at point (i) (5 cm, 0, 0) and (23 cm, 0, 0)
in a region of where there is no other external field. Calculate the electrostatic potential energy of this
charged system.
5. An electric dipole consists of two opposite charges each of magnitude 6 X 10-8 coulomb separated by 6.0cm.
The dipole is placed in an external electric field of 5 X 10-5 NC-1 .
a. What maximum torque will the field exert on the dipole?
b. How much work will an external agent have to do in turning the dipole through 180o, starting from the
position θ = 0o?
UNIT – II : CURRENT ELECTRICITY
FOR UNDER ACHIEVERS
1.
Q.1. Define internal resistance of a cell.
Q.2. what are charge carriers in an electrolytic cell?
Q.3. Name the factors on which internal resistance of cell depends.
Q.4. State the factors on which emf of a cell depend.
Q.5. Differentiate between electromotive force and terminal potential difference.
Q.6. Why the value of emf of a cell is different from the terminal potential difference of cell?
Q.7. Obtain a relation between the emf of a cell, terminal potential difference and internal resistance of the cell.
Q.8. The sequence of bands marked on a carbon resistor are: Red, Red, Red, Silver. Write the value of resistance
with tolerance.
Q.9 Give any two applications super conductors.
Q.10. Prove that current density of a metallic conductor is directly-proportional to the speed of electrons.
Q.11. state the working principle of potentiometer explain with the help of circuit diagram how the emf of two
primary cells are compared by using the potentiometer
Q.12. State Kirchhoff’s law an electrical network. Using the Kirchhoff’s laws deduce the condition for balance in the
Wheat-stone bridge.
Q.13.State the working principle of potentiometer explain with the help of circuit diagram how the potentiometer
is used to determine the internal resistance of the given primary cell.
Q 14 Why manganin used for making standard resistors? Give two reasons.
Q 15 What is drift velocity? Establish the relation between drift velocity and electric current.
Q 16 Define the term resitivity of the conductor. Show that the resistance of the conductor is given by R= ml / ne2ι
A, where symbols have their usual meanings.
Q 17 Draw the colour code scheme of 42kΩ+10℅ carbon resistance.
Q 18 A carbon resistor is marked in coloured bands of red, black, orange and silver. What is the resistance and
tolerance value of the resistor?
FOR AVERAGE STUDENTS
Q.1. A battery of emf ‘E’ and internal resistance ‘r’ gives a current of 0.5 A with an external resistor of 12 ohm and
a current of 0.25 A with an external resistor of 25 ohm. Calculate (i) internal resistance of the cell and (ii) emf of
the cell.
Q.2. ‘n’ identical cells of emf ‘E’ each and internal resistance ‘r’ each are connected in series to an external
resistance ‘R’. Deduce the expression for ‘r’ in terms of total current flowing in the circuit.
Q.3. A 9.0 V battery has an internal resistance of 12.0 .
(a)
What is the potential difference across its terminals when it is supplying a current of 50.0 mA?
(b)
What is the maximum current this battery could supply?
(c)
Draw a sketch graph to show how the terminal potential difference varies with the current
supplied if the internal resistance remains constant. How could the internal resistance be
obtained from the graph?
Q.4. A battery is connected in series with a variable resistor and an ammeter. When the resistance of the resistor is
10 , the current is 2.0 A. When the resistance is 5  ,the current is 3.8 A. Find the emf and the internal
resistance of the battery.
Q.5. Explain why the headlamps of a cargo dim when the starter motor is used.
Q.6. Why manganin is used for making standard resistor?
Q.7. A wire of resistivity ρ is stretched to three times its initial length, what will be its new resistivity.
Q.8. If p.d.V applied across a conductor is increased to 2v, how will the draft velocity of the electrons change?
Q.9. A 10Ω thick wire is stretched so that its length becomes three times. Assuming that there is no change in its
density on stretching, Calculate the resistance of new wire.
Q.10. Two wire of equal length one copper and managing have same resistance , which wire is thicker?.
Q.11. A copper wire of resistivity r is stretched to reduce its diameter to half of its previous value .What will be the
new resistances?
Q.12. You are given 8 Ω resistor. What length of wire of resistance 120 Ωm-1 should be joined in parallel with it to
get a value of 6 Ω ?
Q.13. Three resistance 3Ω,6Ω and 9Ω are connected to a battery. In which of them will the power dissipation be
maximum if a) They all are connected in parallel b) They all are connected in series Give reason.
Q.14. A silver wire has a resistance of 2.1Ω at 27.5˚c and a resistance of 2.7Ω at 100˚c. Determine the temperature
coeff. of resistivity of silver.
Q.15. Two 120V light bulbs , one of 25W and another of 200W are connected in series . One bulb burnt out almost
instantaneously ?.Which one was burnt and why?.
Q.16. A wire of resistance 4R is bend in the form of circle .What is the effective resistance between the ends of
diameter?.
Q.17. Two bulbs whose resistance are in the ratio of 1:2 are connected in parallel to a source of constant voltage.
What will be the ratio of power dissipation in these?
Q.18. Total resistance of the circuit is R/3 in which three identical resistors are connected in parallel. Find the value
of each resistance?.
Q.19. Name the carriers of electric current in
1) a bar made of silver 2) hydrogen discharge tube
3) a
germanium semiconductor 4) a wire made of alloy nichrome 5) super conductor. 6) salt water
Q.20. a potential difference V is applied across the ends of length I and diameter D .what is the effect on drift
velocity of electrons if a) V is doubled b) I is doubled c)D is doubled
Q.21. Draw a graph showing variation of resistivity with temperature for a) nichrome b)silicon
Q.22. A uniform wire of resistance “R” is shaped into a regular “n” sided polygon, where “n” is even. Find the
equivalent resistance between
1) opposite corners of the polygon 2) adjacent corners of the polygon.
Q23. Under what condition is the heat produced in an electric circuit
1) directly proportional 2) inversely
proportional to the resistance of the circuit?
FOR HIGH ACHIEVERS
Q.1. Two cells of emf E1 & E2 have internal resistances r1 & r2. Deduce an expression for equivalent emf of their
parallel combination.
Q.2. Three identical cells each of emf 4V and internal resistance ‘r’ are connected in series to a 6 ohm resistor. If
the current flowing in the circuit is 1.5 A, calculate (i) the internal resistance of each cell and (ii) the terminal
voltage across the cells.
Q.3. Under the conditions will the strength of current in a wire be the same for connection in series and in parallel
of ‘n’ identical cells?
Q.4. Two cells with the same emf and different internal resistances ‘r1’ and ‘r2’ are connected in series to an
external resistance ‘R’. Can a value for ‘R’ be selected such that the potential difference at the first cell should be
zero?
Q.5. A cell of emf ‘E’ and internal resistance ‘r’ is connected across an external resistance ‘R’. Plot a graph showing
the variation of potential difference across ‘R’ verses external resistance’R’.
Q.6. A cell in a deaf aid supplies a current of 25.0 mA through a resistance of 400 . When the wearer turns up the
volume, the resistance is changed to 100  and the current rises to 60 mA. What is the emf and internal resistance
of the cell?
Q.7.A wire of resistance 4R is bend in the form of circle .What is the effective resistance between the ends of
diameter?
Q.8. The variation of potential difference with length in case of two potentiometres A and B is given below.Which
of the two is more sensitive.
Q.9. If the length of the wire conductor is doubled by stretching it , keeping potential difference constant by what
factor the drift speed of the electron changes.
Q.10.A cylindrical metallic wire is stretched to increase its length by 5% . Calculate the Percentage change in
resistances.
Q.11.Two wires A and B have same lengths and same material, have their cross sectional areas 1:4 , what would be
the ratio of heat produced in these wires when the voltage across each is constant.
Q.12.Plot of current I versus time interval is given below. Find the charge that flows through the wire during this
time period
Q.13.A student has two wire of iron and copper of equal length and diameter.He first joins two wires in series and
pass electric current through the combination which increases gradually.After that he joins two wires in parallel
and repeats the process of passing current.Which wire will glow first in each case?
Q.14.Amount of charge passing through the cross section of a wire is q (t)=at2+bt+c.Write the dimensional formula
for a, b and c. If the values of a, b and c in SI unit are 6, 4, 2 respectively. Find the value of current at t=6 seconds.
UNIT 3
“MAGNETIC EFFECTS OF ELECTRIC CURRENT”
LEVEL 1Q1. How much force will be experienced by a moving charge in a magnetic field?
Q2. What is meant by cyclotron frequency?
Q3. What is the effective resistance of ammeter if a shunt resistance S is used across the terminals of the
galvanometer of resistance G?
Q4. Which physical quantity has the unit Wb/m2? Is it a scalar or a vector quantity?
Q5. If magnetic dipole is along the direction of magnetic field. What is the potential energy? If it is rotated by 180°,
then what amount of work will be done?
Q6. What is the angle of dip at a place where horizontal & vertical components of Earth’s magnetic field are equal?
Q7. Why do magnetic lines of force prefer to pass through iron than air?
Q8. Which material is used for making permanent magnet & why?
Q9. Where is the magnetic field due to a current carrying solenoid remains uniform?
Q10. Which material is used for making electromagnet and why? Ans10. For making electromagnet, a material
having low coercivity is used, & soft iron has low coercivity So, soft iron is preferred.
Q11. What is the net magnetic moment of an atom of a diamagnetic material?
Q12. Give two points of difference between magnetic properties of soft iron and steel.
Q13. What is the main function of soft iron core used in moving coil Galvanometer?
Q14. What happens if an iron bar magnet is melted? Does it retain magnetism?
LEVEL 2Q1. A beam of electrons projected along +X axis, experiences a force due to a magnetic field along +Y axis. What is
the direction of magnetic field?
Q2. Why should the spring/suspension wire in a moving coil galvanometer have low torsion constant?
Q3. For a Para magnetic material, plot the variation of intensity of magnetisation with temperature.
Q4. A particle with charge q moving with a velocity v moving in the plane of paper enters a uniform magnetic field
B acting perpendicular to paper and pointing inwards. Why does the kinetic energy of the charge particle not
change while moving in the field?
Q5. How will the magnetic field strength at the centre of the circular coil carrying current change, if the current
through the coil is doubled and radius is halved?
Q6.Can moving coil galvanometer be used to detect an a.c. in a Circuit? Give reason.
Q7. Deduce an expression for the magnetic dipole moment of an electron orbiting around the central nucleus.
Ans7. Refer to page no 162 Part-1 of NCERT.
Q8. Using Ampere’s circuital law, derive an expression for magnetic field along the axis of a current carrying
toroidal solenoid of N number of turns having radius r.
Q9. Define the terms magnetic inclination and horizontal component of earth’s magnetic field at a place. Establish
the relation between them.
Q10. A galvanometer has a resistance of 30Ω. It gives full scale deflection with a current of 2 mA. Calculate the
value of resistance needed to convert it into an ammeter of range 0-0.3A.
Q11. Derive an expression for magnetic field on the axial line of circular loop of radius ‘a’ and carrying current I at a
distance x from the centre.
Q12. A rectangular coil of N turns and area of cross section A is placed in uniform magnetic field B with area vector
making angle with B. Derive an expression for torque on the coil.
Q13. Draw a schematic sketch of a cyclotron. Explain briefly how it works and how it is used to accelerate the
charged particle i) Show that the time period of ions in a cyclotron is independent of both the speed and radius of
circular path. ii) What is resonance condition? How is it used to accelerate the charged particle?
Q14. Two straight long parallel conductors carry currents I1 and I2 in the same direction. Deduce an expression for
the force per unit length between them.
Q15. a) With the help of a diagram, explain the principle and working a moving coil galvanometer. b) What is the
importance of radial magnetic field and how is it produced. c) While using moving coil galvanometer as a
voltmeter a high resistance in series is required whereas in an ammeter a shunt is used. Why?
Q16. Derive an expression for the magnetic field along the axis of air cored solenoid, using Ampere’s circuital law.
Sketch themagnetic field lines for a finite solenoid. Explain why the field at exterior is weak while at the interior it
is uniform and strong.
LEVEL 3
Q1.A charged particle moving in a uniform magnetic field penetrates a layer of lead and thereby loses one half of
its kinetic energy.How does the radius of curvature of its path change?
Q2. Why diamagnetism is almost independent of temperature?
Q3. Three identical specimens of magnetic materials nickel, antimony and aluminium are kept in a uniform
magnetic field. Draw the modification of field lines in each case. Justify your answer.
Q4. How can a moving coil galvanometer be converted into an ammeter? To increase current sensitivity of a
moving coil galvanometer by 50% its resistance is increased so that the new resistance becomes twice its initial
resistance. By what factor does its voltage sensitivity change?
Q5.Two small identical circular loops, marked (1) and (2), carrying equal currents, are placed with the geometrical
axes perpendicular to each other as shown in figure. Find the magnitude and direction of the net magnetic field
produced at the point O.
Q6.Two protons P and Q moving with the same speed enter magnetic fields B 1 and B2 respectively at right angles
to the field directions. If B2 is greater than B1, for which of the protons P and Q, the circular path in the magnetic
field will have a smaller radius?
Q7. An electron and a proton moving parallel to each other in the same direction with equal momenta enter into a
uniform magnetic field which is at right angle to their velocities. Calculate the ratio of radii of the circular path.
Under achiever student
1-Write S.I. unit of magnetic flux?
2-Is magnetic flux a scalar or vector quantity?
3-Define the term self inductance of a coil.give its S.I.unit.
4-Define one henry.
5-State lenz~s law
6 -Define mutual inductance.
7-what is the phase difference between the voltages across the inductance and capacitor in an a.c.circuit
8-does current induce in a coil depend on its resistance.
9-on what factors does the self inductance of a solenoid depend?
10-what is wattles current?
11-what is the working principle of transformer?
12-what is the resistance offered by capacitance to D.C.?
Average student
1-how does the self inductance of an air coil change when
a-no of turn of the coil decreases
b-an iron rod is introduced in the coil.
2-if the no of turns in the solenoid is doubled keeping other factors constant, how does the self
inductance of the coil change?
3- a bar magnet falls from a height h through a metal ring. will its acceleration be equal to ‘g’.
Give reason for your answer.
4- if the rate of change of current 2 amp/sec induces an emf of 40mV in the solenoid, what is the
self inductance of this solenoid.
5-why does a metallic piece become very hot when it is surrounded by coil carrying high frequency
A.C.
6. Define self-inductance and give its S.I. unit. derive an expression for self inductance of a long air-cored
solenoid of length l, radius r and having N number of turns.
7. With the help of a labelled diagram, explain the principle, construction and working of an a.c.
generator. Derive the expression for induced e.m.f.
8. Explain with the help of a labeled diagram, the principle, construction and working of a transformer.
Why is its core are laminated?
9. Using phasor diagram, derive an expression for the impedance of a series LCR circuit. What do you
mean by resonance condition of such a circuit?
10. What do you mean by sharpness of resonance in a series resonance circuit. Find an expression for Qfactor of the circuit.
BRIGHT STUDENTS
1. Prove that an ideal capacitor connected to an a.c. source does not dissipate any power.
2. What is meant by root mean square value of an alternating current.
3. An ordinary moving coil ammeter used for d.c. cannot be used to measure an alternating current even
if its frequency is low. explain, why?
4.i) Draw the graphs showing the variation of inductive reactance and capacitive reactance with
frequency of applied a.c. source. (ii) can the voltage drop across the inductor or the capacitor in a series
LCR- circuit be greatar than the applied voltage of the a.c. source ? Justify your answer.
5. An alternating voltage E =200sin300t is applied across a series combination of R=10Ω and an inductor
of 800 mH . calculate
(i) impedance of the circuit
(ii) peak value of current in the circuit
(iii) power factor of the circuit
6. A sinusoidal voltage of peak value of 283V and frequency 50Hz is applied to series LCR circuit in which
R=3Ω, L=25.48mH, C=796µF. Find (a) the impedance of the circuit, (b) the phase difference between the
voltage across the source and the currents ,(c) the power dissipated in the circuit and (d) the power
factor.
7. When a series LCR –circuit is brought into resonance, the current in the circuit increases to a large
value. Why?
8. What is copper loss in a transformer?
9. Why is the core of a transformer made of a magnetic material of highpermeability?
10. Which is the best method of reducing current in an a.c. circuit and why?
BELOW ACHEIVER STUDENT (LEVEL -1)
1.
How does reflection differ from refraction?
2.
What causes the light ray to change direction when it suffers refraction?
3.
Light travels more quickly in vacuum than in clear plastic. Which will have the greater angle with the normal?
4.
Suppose light travels from air into glass (where it travels slower). Is its wavelength greater in the air or in the
glass?
5.
What conditions are necessary in order for the phenomenon of total internal reflection to occur?
6.
What phenomenon causes us to see the sun after it has set below the horizon?
7.
Are mirages caused by reflection or refraction?
8.
Blue light travels slower than yellow light in glass. Which of the two colours will be bent more by a glass prism?
9.
What phenomenon causes rainbows?
10. If you are to see a rainbow at sunrise, what direction must you look?
11. Does light travel faster in crown glass or in flint glass?
12. Is the critical angle for diamond greater or less than that for glass?
13. What is the critical angle for (i) diamond-air boundary (ii) glass-air boundary?
14. What is a light pipe? Why does not the light leave the light pipe?
15. Mention the factors that influence the focal length of a lens.
16. Is a real or a virtual image formed by a diverging lens?
17. What type of lens can be used as a magnifier?
18. In a microscope, (i) if the image formed by the objective is 25 times as far from the lens as is the object, what
magnification does this lens produce? (ii) If the final image is 10 times as far from the eyepiece as is its object (the
image formed by the objective), then what is the magnification as a whole?
19. What is the advantage of a telescope with a large objective lens?
20. Suppose a converging lens forms an image of a very distant object. Where is the image located?
21. As a distant object moves closer to the lens, what happens to the position of the image?
22. An object is 23 cm from a lens and the magnification produced by the lens is 3. Where is the image located 'f
23. How does the eye accommodate (focus on objects at different distances)?
24. Name the two most common vision defects. What type of lens is used to correct each?
25. What is the difference between real and virtual images?
26. How does the focal point of a converging lens differ from the focal point for a diverging lens?
27. How do converging lenses and diverging lenses differ in their appearance and in what they do to a beam of
parallel light?
28. What differs light waves which result in the phenomenon of colour?
29. Why does the light appear to travel in straight line inspite of its wave nature?
30. Can two independent sources of light produce interference?
31. In Young's double slit experiment, the monochromatic source of light is replaced by white light source. What
would be the colour of the central fringe?
32. Is the fringe width for dark fringe different from that of bright fringe?
33. What happens to the interference pattern when the entire arrangement of double slit experiment is dipped in
water?
34. When two light waves interfere, then at some points there is darkness. Where does the light energy of
these points go? Does the phenomenon of interference of light violate law of conservation of energy?
35. Light from two coherent sources is reaching a screen. If the path difference at a point on the screen for the
yellow light be
3
, then what will be the colour of the fringe at that point?
2
36. Does diffraction of light take place at the two slits in the Young's interference experiment?
37. What is the difference in the origin of colours of a soap bubble seen in sun's light and the colours emerging
from a prism?
38. Is polarization possible in longitudinal waves? If not, why?
39. Does the value of polarising angle for a transparent medium depend upon the wavelength of the light?
40. What is the special utility of sun goggles made of Polaroids instead of coloured glass?
FOR AVERAGE STUDENT (LEVEL-2)
1.
Two coherent sources emit waves of amplitudes a & 2a. They meet at a points P equidistant from the two
sources .If the intensity of the first is I, What is the resultant intensity at point P?
2.
Consider the interference between two sources of intensities 4I & I. Obtain the intensity at a point where the
phase difference is (a)  (b)  / 2.
3.
In young’s double slit experiment, the intensity of central maximum is I. what will be the intensity at the same
place if one slit is closed?
4.
Why does a soap bubble show beautiful colours when illuminated by white light?
5.
Why do we fail to observe the diffraction from a wide slit illuminated by monochromatic light?
6.
A single slit diffraction pattern is completely immersed in water without changing any other parameter. How
is the width of central maximum affected?
7.
Geometrical optics is based on the assumption that light travels in a straight line. Diffraction effects disprove
this assumption. Yet the geometrical optics assumption is so commonly used in understanding location and
several other properties of images in optical instruments. What is the justification?
8.
Name one such phenomenon that is shown by light waves but not by sound waves.
9.
State Malus law.
10. A polariser and analyser are so oriented that no light is transmitted. What is the angle between the axes of
polariser and analyser?
11. Write two simple uses of Polaroid
12. Is backward wavefront possible? Give reason in support of your answer.
13. Show that a plane wavefront incident on concave mirror is reflected as a spherical wavefront.
14. Can two independent light sources produce interference? Explain.
15. Show that the phenomenon of interference of light is in accordance with the law of conservation of energy.
16. Describe the diffraction of light at a single slit. Explain the formation of pattern of fringes.
17. What is polarisation by reflection? Deduce Brewster law.
18. State Brewster law. Use it to show that at the polarising angle of incidence, the reflected and transmitted rays
are perpendicular to each other.
19. State Raleigh’s law of scattering.
20. Why does the sky appear blue? What will it look like on the moon?
21. What is the cause of blue colour of ocean?
22. How do you account for the red colour of the sun during sunrise and sunset?
23. When is the liner magnification equal to angular magnification?
24. If the final image is formed at infinity, what is the magnification of a simple microscope?
25. Why should the objective of a telescope have a larger focal length?
26. Ray optics as a limiting case of wave optics. Comment.
27. A straight rod appears bent in water. Why?
28. State the advantages of totally reflecting prisms over plane mirrors.
29. A convex lens made up of a material of refractive index 1 is immersed in medium of refractive index ’2 .
Trace the path of a parallel beam of light passing through the lens when (a) 1<2 (b) 1=2 explain your
answer.
30. A concave mirror and a concave lens are held in water. What changes, if any do you expect in their respective
focal lengths as compared to their values in air?
31. Distinguish between magnifying power and resolving power of a microscope.
32. Define the terms magnifying power and resolving power of a Telescope.
33. Draw a labelled diagram of an astronomical telescope forming the final image at the near point. Write down
the formula for its magnifying power.
34. Why is the resolving power of a microscope having oil immersion objective high?
35. Establish the relationship between object distance, image distance, and radius of curvature for convex mirror.
36. Derive lens maker’s formula from curved surface formulae.
37. Derive the expression for the angle of deviation for a ray of light passing through an equilateral prism of
refractive angle `A’.
38. With the help of a ray diagram, explain the construction and working of a reflecting telescope.
39. What is importance of Huygens’s principle?
40. When monochromatic light is incident on a surface separating the two media, the reflected and refracted
lights both have the same frequency? Explain why?
41. Is speed of light is independent of the colour of light? If not, which of the two colours (red and violet) travels
slower in a glass prism?
42. Out of electric field vector E and magnetic field vector B in an electromagnetic wave, which is more effective
and why?
43. Why it is not possible to detect interference pattern, when the two coherent sources are far apart?
44. Can white light produce interference? What is the nature?
45. If one of the slits in Young’s double slit experiment is painted so that it transmits half the light intensity of the,
then what will be thee effect on the intensities of maxima and minima in the interference pattern?
46. Light from two coherent sources is reaching on a screen. If the path difference at a point on the screen for the
yellow light were 3/2,then what will be the colour of the fringe at that point? Explain with necessary
argument:
47. In young’s experiment the double slit is first covered by the red cellophane paper and then by blue. What
change will be observed in the fringe width?
48. In a single-slit diffraction experiment, the width of the slit is made double the original width. How does this
affect the size and intensity of the central diffraction band?
49. How does the polarization afford a convincing evidence of the transverse nature of light?
50. Two Polaroid’s are placed at 90 to each other and transmitted intensity is zero. What happens when one
more Polaroid is placed between these two, bisecting the angle between them?
DUAL NATURE OF MATTER AND RADIATIONS
1. If wavelength of electromagnetic waves are doubled what will happen to energy of
photon?
2. Alkali metals are most suitable for photoelectric emission. Why?
3. Out of microwaves, UV, IR which radiation will be most effecting for emission of
electrons from a metallic surface?
4. Can X-rays cause photoelectric effect?
5. If the intensity of incident radiation on a metal is doubled what happens to the K.E of
electrons emitted?
6. What is the value of stopping potential between the cathode and anode of photocell? If the
max K.E of electrons emitted is 5eV?
7. It is easier to remove an electron from sodium than from copper, which has a higher value
of threshold wavelength?
8. What is the role of photocell in cinematography?
9. An electron and photon possessing same K.E. Which one will have greater wavelength?
10. In Davisson – Germer experiment if the angle of diffraction is 520 find Glancing angle?
11. What is the energy associated with a photon of wavelength 6000 A0 ?
12. What is the effect on the velocity photo electrons, if the wavelength of incident light
is decreased?
13. Show graphically how the stopping potential for a given metal varies with a frequency of
the incident radiation.
14. To work functions 2ev and 5ev for two metals x and y respectively. Which metal will emit
electrons,
when it is irradiated with light and wave length 400nm and why?
15. A photon and an electron have same de-broglie wavelength. Which has greater total
energy.Explain?
16. The de-broglie wave length of a photon is same as the wave length of electron. Show that K.E. of a
photon is 2mc ‫ג‬/h times K.E. of electron. Where ‘m’ is mass of electron,c is velocity of light.
17. Derive the expression of de-broglie wave length in terms of energy of energy and temperature?
18. Light from bulb falls on a wodden table but no photon electrons are emitted why ?
19. Following table gives values of work function for a few photosensitive metal.
S.NO Metal
Work function(ev)
1
Na
1.92
2
K
2.15
3
Mo
4.17
If each metal is exposed to radiation of wavelength 300nm , which of them will not emit photo
electron.
20. An electron and alpha particle and proton have same kinetic energy , which have shortest
De-broglie wavelength?
21. The De-broglie wave length associated with proton and neutron are equal.Which has
greater kinetic energy?.
22. A stream of electron travelling with a speed at right angle to a uniform electric field E, is
deflected in a circular path of radius “r” . Prove that e/m = v2/rE.
23. If the potential difference used to accelerate electron is doubled , by what factor the Debroglie
wave length of the electron beam changed.
24. The De-broglie wave length associated with an electron accelerated through the potential
difference “V” is λ. What will be its wave length , when accelerating potential is increased to 4v?
25. Visible light cannot eject photo electrons from copper surface, whose work function is 4.4 ev , why?
Prove mathematically.
EXTRA QUESTIONS
1. Neutrons, in thermal equilibrium with matter have an average KE = 3/2 kT .Compute de-Broglie’s
wavelength associated
2. A nucleus of mass M initially at rest splits in two fragments of masses M/3 & 2M/3. Find the ratio
of de-Broglie’s wavelength of two fragments.
3. X-rays of wavelength 0.82 A0 fall on metallic surface. Calculate de-Broglie’s wavelength of
emitted photoelectrons. Ignoreof the metal.
4. Wavelength of photon and de-Broglie’s wavelength of electron has same value. Show that
energy of photon is 2mc/h times the KE of electron.
5. Compare energy of electron of de-Broglie’s wavelength 1 A0 with that of an X-ray photon of the
same wavelength.
6. Calculate the ratio of de-Broglie wavelength associated with deutron moving with velocity ‘2v’
and a -particle moving with velocity ‘v’.
7. An -particle and proton are accelerated from rest through same PD ‘V’. Find the ratio of deBroglie wavelength associated with them.
8. Calculate de-Broglie’s wavelength associated with an electron of energy 200eV. What will be the
change in if accelerating potential is increased to 4 times.
9. What is the (i) momentum (ii) speed and (iii) de-Broglie wavelength of electron of kinetic energy
120 eV.
10.Show that the wavelength of electromagnetic radiation is equal to the de-Broglie wavelength of
its photon.
11. An electron, -particle and a proton have same KE. Which of these particles have shortest
wavelength?
12. The threshold frequency for a certain metal is 3.3*1014 Hz. If light of frequency 8.2*1014 Hz is
incident on the metal. Predict the velocity of ejected electrons and cut-off voltage.
13.The work function of two metals A and B are respectively 1.2 eV and 2.4eV. Light of wavelength
600nm falls on these metals.(i) Which metal / metals will give photoelectric emission?
(ii) What is the maximum velocity and cut-off potential?
(iii) If the source is moved away, how does it affect the stopping potential?
14. The energy flux of sun reaching the earth is 1.3888*103 Wm-2. How many photons per square
m is incident on the earth per sec. Assume average wavelength of sunlight = 550nm.
15. In an experiment on photoelectric effect, the slope of cut-off voltage versus frequency of light is
found to be 4.12*10-15 Vs. Calculate the value of Plank’s constant.
16.The Photoelectric cut-off voltage for certain metal is 1.5V. What is the maximum KE of
photoelectrons?
17. The threshold frequency of metal is ‘f’. When the light of frequency 2f is incident on it the
maximum velocity of photoelectrons is ‘v1’. When the frequency is increased to 5f, the maximum
velocity of photoelectrons is ‘v2’ Find v1 /v2.
18.The work function of cesium is 2.14 eV. Find (i) threshold frequency (ii) wavelength of light if the
photoelectrons are stopped with stopping potential 0.6V.
19.In a plot of photoelectric current versus anode potential, how does a. the saturation current
vary with anode potential for incident radiations of different frequencies but same intensity.
b. The stopping potential varies for incident radiations of different intensities but same frequency?
c. Photoelectric current vary for different intensities but same frequency of incident radiations?
Justify your answer in each case.
20. The radiations of frequency 1015 Hz are incident on two photosensitive surfaces A and B.
Following observations are recorded:
Surface A: no photo electric emission takes place.
Surface B: Photoemission takes place photo electrons have zero energy.
Explain the above observations on the basis of Einstein’s photoelectric equations. How will the
observations with surface B change when the wavelength of incident radiations is decreased?
21. An electron, -particle and a proton have same de-Broglie wavelength. Which of these particles
has (i) minimum KE and (ii) maximum KE and why? In what way has the wave nature of electron
beam exploited in electron microscope?
22.Calculate the (i) momentum and (ii) de- Broglie wavelength of electron accelerated through a
potential difference of 56 V. On increasing the potential how this can improve the resolving power
of a microscope.
23. Light of frequency 2.5 0 is incident on surface of threshold frequency 0 and the photoelectric
current is 1 mA. If frequency of light is halved and intensity is doubled, find new photoelectric
current.
24. For what KE of neutron, will the associated de Broglie wavelength be 1.32*10-10 m?
25.The work function of three metals Na, K and Mo are respectively 1.92, 2.15 and 4.17 eV. If each
of the metal is exposed to light of wavelength 300 nm, which of them will not emit photoelectrons
and why?
26.By how much would the Stopping Potential afor given surface goes up if the frequency of the
Incident radiation were to be increased from 4
1015Hz to 8 1015Hz?
27. Calculate de-Broglie wave length of (i) an electron (mass 3 10 –2 kg moving with speed 100
m/s. Hence show that wave nature in hydrogen atom) moving with speed 1/100
of speed of light in vacuum and (ii) a ball of radius 5 mm and of matter is important at atomic level
but is not really relevant at the macroscopic level.
28.The de-Brouglie wavelength associated with proton and a neutron is found to be equal. Which
of the two has higher value of kinetic energy?
29. Graph showing variation of VS with frequency for two M1, M2 material is given.
(i) What are the values of work function for M1 and M2 VS (ii)The values of VS for these for
frequency 3 ( 3 > 02) are V1 and V2. Show that slope of lines equals V1 - V2) / ( 02 - 01) 01
02
30.Through what potential difference should an electron be accelerated so that its de-broglie
wavelength becomes 0.4 Ao.
31.Monochromatic light of frequency 6x1014 Hz is produced by a LASER. The power emitted is
2x10-3 W. a) What is the energy of photon in the light beam. b) How many photons per sec on the
average are emitted by the source. [Ans. (a) 2.49 eV, (b) 5x1015 sec-1]
32.If 5 % of the energy supplied to an incandescent light bulb is radiated as visible light, how many
visible quantas are emitted by a 100W bulb? Assuming the wavelength of all the visible light to be
5000 Ao. [Ans. 1.41x1019 J]
33.If the wavelength of incident light changes from 4400 Aoto 4000 Ao, then find the change in
stopping potential. [Ans. -0.26 eV]
UNIT-VIII
ATOMIC NUCLEUS
1) what conclusions were drawn from the observation in which few alpha-particle were seen
rebounding from gold foil?
2) which observation led to the conclusion in the α-particle scattering exp. That atom
has vast empty space?
3) Compare the radii of two nuclei with mass number 1 and 27 respectively.
4) Two nuclei have mass numbers in the ratio 1:8.What is the ratio of their nuclear
radii?
5) which have greater ionizing power:α-particles or β-particles?
6) The half life of a radioactive substance in 30 days. What is the time taken for ¾
of its original mass to disintegrate?
7) Why neutrons are considered as ideal particle for nuclear reactions?
8) Does the ratio of neutrons and protons in the nucleus increase, decreases or
remain the same after the emission of ά – particles?
9) Why is the ionization power of ά – particle of greater than γ – rays?
10) A radio isotope of silver has a half life of 20 minutes. What fraction of the
original mass would remain after one hour?
11) What changes takes place in the nucleus when a γ – rays is emitted?
12) Can a single nucleus emit ά – particle, β – particle and a γ – rays together?
13) Two nuclei have mass no. in the ratio 1:2. What is the ratio their nuclear
densities?
14) Establish the relationship between half life of a radio- active substance and
decay
constant.
15) Explain how ά particle scattering experiment led to Rutherford to estimate the
size of the
nucleus.
16) The activity of a radio active material drops to 1-16th of its initial value in 30
days. Find its
half life.
17) In a particular fission reaction, a U 235 nucleus captures a slow neutron. The
fission products are 3 neutrons, a La 142 and fission products X y z .What is
the value of Y and Z.
18) You are given two nuclides X
b) Which one of the two is likely to be more stable? Give reason.
19) A certain radio active substance has a half life of 30 days. What is the
disintegration
constant? Find its average life.
20) Find the time required to decay 3/4th of a radioactive sample whose half life is
60 days.
21) Neon -23 decays in the following way
23Ne10 --------------- 23Na11 + 0e-1 +γ
Find the minimum and maximum kinetic energy that the β-particle can have.
The atomic masses of 23Ne10 and 23Na11 are 22.99454 and 22.98984
respectively.
22) The disintegration rate of a certain radioactive sample at any instant is 4750
disintegrations per minute. Five minutes later the rate becomes 2700 per
minute. Calculate
a) Decay constant
b) Half-life of the sample
23) Explain with an example, whether neutron-proton ratio increases or
decreases during beta decay.
24) The half life period of radioactive element A is the same as the mean half time
of another radioactive element B.Initially both of them have the same number of
atoms. The radioactive element B decays faster than A. Explain why?
25) Obtain the binding energy of a nitrogen nucleus from the following data
mh=1.007834; mn=1.00867; mN=14.03074
Give your answer in MeV.
26) Write nuclear equations for
a) The α-decay of 226Ra88
b) The β- -decay of 32P15
c) The β+ decay of32P15
27) A neutron is absorbed by a 6Li3 nucleus with the subsequent emission of an
alpha particle.
i) Write the corresponding nuclear reactions.
ii) Calculate the energy released in MeV, in this reaction.
Given mass 6Li3=6.0151264; mass (neutron) =1.00966544
Mass (alpha particle)=4.00260444 and mass(triton)=3.01000004
Extra Questions
1. Calculate the energy released in the following nuclear reaction.
3 Li 7 + 0 n 1 2 He 4 + 1 H 3
2. When a deutron of mass 2.0141amu is absorbed by a 3 Li 6 nucleus of
mass 6.015amu, the nucleus splits into two -particles each of mass
4.0026amu. Calculate energy carried by each -particles.
3. A nucleus 10 Na 23 undergoes -decay to give 11 Na 23. Write down the
nuclear reaction. Calculate KE of electron. Given mass of 10 Na 23 =
22.994466amu, mass of 11 Na 23 = 22.989770amu.
4. A neutron is absorbed by 3 Li 6 nucleus with the subsequent emission of a
-particle. (i) Write the corresponding nuclear reaction.
(ii) Calculate the energy released. M 3Li6 = 6.015126amu, m(n) =
1.0086654amu, mass of triton = 3.0100000amu.
5. The mass of the star is 5 * 1032 kg. It generates energy at the rate of 5 *
1030 W. How long does it take to convert all Helium to carbon at this rate.
3 2 He 4 6 C 12 + 7.27 MeV
6. Prove mathematically that the fraction N / N0 of a radioactive element left
over after a time ‘t’ equals 1 / x where x = 2 t/T. T is half-life period.
7. The radioactive nuclei X and Y contain equal number of atoms. Their
half-life periods are 1 H and 2 H respectively. Calculate the ratio of their
activity after 2 Hrs.
8. How many disintegrations per sec will occur in one gm of 92 U 238, if its
half-life period is 1.42 * 10 17 sec.
9. A radioactive sample contains 2.2mg of pure 6 C 11, having half-life
period 1224seconds. Calculate (i) Number of active atoms
(ii) Activity when 5 gm of sample is left.
10. The half-life period of 92 U 238 against -decay is 4.5 * 109 years. What is
the activity of 1g sample?
11. Obtain the amount of 27 Co 60 necessary to provide a radioactive source of
8 mC. The half-life period of Co60 is 5.3 years.
12. A 12.5 MeV -particle approaching a gold nucleus is deflected back by
1800.
How close does it approach the nucleus
15. Calculate half-life period and decay constant 1.0
.75
0.5
0.25
70 140 210 280 time (days)
16. The half-life period of radioactive sample is 5500 years. Its initial
activity is
found to be 15 decays per min per gram. In how much time would its
activity reduces to 10 decays per min per gm? (Given loge3 = 1.0986 and
loge2 0.693)
17. The decay constant for a given radioactive sample is 0.3465 days-1. What
% of this sample gets decayed in a period of 4 days?
18. The nucleus 92U238is unstable against -decay with a half-life of about
4.5x 109 years. Write down the equation of this decay and estimate the
KE of emitted -particle from the following data {m (92U238 = 238.05081
amu, m (2 He4 = 4.00260 amu, m (90
Th234 = 234.04363 amu}
(4.19 MeV)
19. How many and particles are emitted when 92U238 changes into 82Pb206.
20. The energy level of an atom of element X is given below.
Which one of the level transitions results in the emission of photon of
wavelength 620 nm. Justify your answer with proper calculation
0
-1 eV
ABC
-3 eV
DE
-10 eV
20. Calculate the longest and shortest wavelength of Lyman series. Given R =
10967700 m-1. (911.6 A0, 1215 A0)
21. The wavelength of second line of the Balmer series in hydrogen spectrum
is 4861 A0. Calculate the wavelength of first line. (6562 A0)
22. Which state of the triply ionized beryllium atom (Be +3) has the same
orbital radius as that of the ground state of hydrogen atom? {rn n2 /Z}
Ans n = 2.
23. Which level of double ionized lithium (Li +2) has same energy as the
ground state energy of hydrogen atom? Compare the orbital radius of two
levels. {En Z2 / n2)
24. Calculate the frequency of photon, which can excite the electron to – 3.4
eV from – 13.6 eV. (2.47 1015 Hz)
25.Show that the shortest wavelength lines in Lyman, Balmer and Paschen
series have their wavelength ratio 1: 4: 9.
26.The potential energy of the electron in ground state is –27 eV, what is its
potential and kinetic energies?
27.Show that the wavelength of electromagnetic radiation is equal to the de
Broglie wavelength of its photon.
28. A radioactive sample has N0 nuclei at t = 0. Its no. of undecayed nuclei
get reduced to N0 /e at t = . What does the term stand for? Write in
term of the time interval ‘T’ in which half of original number of nuclei,
of this radionucleide would have got decayed?
29. If the nucleus 26Fe56 splits into two nuclei of 13Al28. Would the energy be
released or needed for this process to occur? Also calculate this energy.
Given m (26Fe56) = 55.93494 amu, m(13Al28 ) = 27.98191 amu.
30.Calculate the ratio of energies of photon due to transition of electron of
hydrogen atom from (i) second permitted energy level to first level (ii)
highest permitted energy level to second permitted level.
31. Prove that the instantaneous rate of change of activity of a radioactive
substance is inversely proportional to the square of its half-life period.
32. The nucleus of an atom 92Y235 initially at rest decays by emitting an particle as per equation 92Y235 90X231 + 2He4 + energy. It is
given that BE per nucleon of parent and the daughter nuclei are 7.8 MeV
and 7.835 MeV and that of -particle is 7.07 MeV / nucleon. Assuming
the daughter nucleus to be formed in unexcited state and neglecting its
share of in energy of the reaction, calculate the speed of emitted particle. Take mass of -particle = 6.68 10-27 kg.
33. Four nuclei of an atom fuse together to form a heavier nucleus. If the
process is accompanied by release of energy, which of the two parent or
daughter nucleus have higher BE/nucleon?
34.The spectrum of a star in the visible and the ultraviolet region was
observed and wave-length of some of the lines were identified were
found to be
824 A0, 970 A0, 1120 A0, 2504 A0, 5173 A0, 6100 A0
Which of these lines cannot belong to hydrogen atom spectrum.
(Given R = 1.03 107 m-1) and 1 / R = 970 A0. Support your answer
with proper calculation.
35. Why a nucleus can eject electron (B particle) though it contain no
electron?
36.Why nucleuses have mass less than the sum of masses of individual
nucleons in them?
37.How wills the distance of closest approach changes: a) when the kinetic
energy is of the projectile is doubled? B) when the velocity of projectile
is halved.
38. The second member of Lyman series in hydrogen spectrum has
wavelength 5400 Ao. Find the wavelength of first number.
39.What is the effect of temperature and pressure on the radioactivity?
40. What is the value of impact parameter of alpha particle scattered through
an angle of 180o.
41.Draw the graph showing the distribution of electron’s emitted during beta
decay.
Question Bank---Semiconductor Devices
Group---7(Maxwell)
5 Marks questions.
1.
2.
3.
4.
Level 1
1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
Level 2
Explain the formation of energy bands in solids. Distinguish between conductors, extrinsic
and intrinsic semiconductors and insulators on the basis of band theory.
Explain with the help of labeled ckt diagram, the use of NPN transistor as an amplifier in C-E
configuration. Input resistance of transistor is 100ohm.On changing its base current by
10µA.The collector current increases by 2mA. If a load resistance of 5kohm is used in the ckt.
Calculate a) current gain b) voltage gain of the amplifier.
Explain working of a transistor as an oscillator.
What is the function of emitter, base and collector in a junction transistor. Explain with the
help of a suitable diagram the use of npn transistor as a switch.
3 marks questions
Draw energy band diagram for intrinsic, n-type and p-type semiconductors.
Explain the formation of depletion layer in a junction diode. How is it affected by doping level?
What is a Zener diode? Draw symbol for it. How is it used as a voltage regulator?
Write one disadvantage of a half wave rectifier. Explain the working of a full wave rectifier with the help
of a diagram.
A pure semiconductor is doped with In and As respectively one by one. Give the nature of charge carrier
in the two, justify your answer.
Name the different types of diodes and write one application of each.
Explain action of an n-p-n transistor in C-E configuration.
Explain working of a transistor as an amplifier.
Explain working of a transistor as an oscillator.
Explain OR, AND & NOT gate with respect to their symbols and truth tables.
1) Draw energy band diagram for semiconductors, insulators and conductors. On the basis of these diagram
explain the difference b/w them.
2) Draw the circuit diagram for a p-n diode
i)
When it shows low resistance
ii)
When it shows high resistance.
iii)
Draw I-V characteristics in the two cases.
3) Explain with the help of a diagram the different processes that takes place when a p-type and n-type
semiconductor joined together.
4) Name the diode used in a voltage regulator. Draw the necessary circuit diagram to explain its use in a
voltage regulator.
5) Explain how are LED and photo diode biased? How does working differ from each other? Write one
application of each.
6) Draw circuit diagram for p-n diode as a rectifier and explain its working.
7) Draw a circuit diagram to obtain I-V characteristics of an n-p-n transistor in C-E configuration.
8) Explain with the help of a circuit diagram the working of a transistor as an amplifier and write different
gains.
9) Draw symbols for OR, AND &NOT gate and also write their truth table.
10) Explain different processes involved in the working of a solar cell.
Level 3
1) Distinguish b/w extrinsic and intrinsic semiconductor.
2) Output of an unregulated d.c. voltage supply is to be regulated. Name the device that can be used for this
purpose and draw the necessary circuit diagram.
3) Distinguish b/w an LED and a photo diode. Draw their biasing circuits.
4) How does a full wave rectifier differ from a half wave rectifier? Explain the working of a full wave rectifier;
name the circuit to smoothen out the output of rectifier.
5) Explain with the help of diagram the principle of an oscillator. What type of feedback is used in an
oscillator?
6) Explain the action of a transistor as a switch.
7) The base current of a transistor is 105µA and collector current is 2.05mA
a) Determine the value of the emitter current and current gain
b) A change of 27µA in the base current produces a change of 0 .65mA in the collector current find β a.c.
8) Explain
i)
Using NAND gate only how will you get AND & OR gate.
ii)
Using NOR gate how will you get OR and AND gate.
2Marks questions:1)
Give the symbol of OR, AND, NOT gate.
2)
Give the truth table of OR, AND gate.
3)
Distinguish between n-type and p-type semiconductor with suitable energy band diagram.
4)
Draw the characteristics of forward and reverse biased p-n junction.
5)
Define potential barrier.
6)
Why is NAND gate called a universal gate.
7.)
How two input AND gate can be converted into NAND gate?
8)
In C-E ckt,if Vce is changed by .2 volt,Ic changes by 0.004mA. Calculate the output resistance.
9)
What will happen if emitter as well as collector in a transistor is reverse biased.
10)
Can two p-n junction diode placed back to back work as a pnp transistor.
11)
What is the ratio of negativcharge to positive charge in a n-type semiconductor.
12)
A photo diode is fabricated from a semiconductor of band gap of 2.8eV can it detect a wavelength of
600nm. Justify.
13)
The base current of a transistor is 105
change in Ie by 2.7
and the collector current is 2.05mA. Determine α, β and Ie. If a
produces a change of 0.65mA in Ic. Determine βac.
14)
If the frequency of the input is 50Hz. Find the frequency of output in full wave and half wave rectifier.
15)
Why is the base region in a transistor is taken thin and lightly doped
One mark Questions:1)
2)
3)
4)
5)
6)
7)
8)
9)
10)
11)
12)
13)
14)
15)
What are holes?
Define doping.
What are the minority charge carriers in p-type and n-type semiconductor?
What do you mean by biasing?
What is a solar cell?
What is the full form of LED?
Find the ratio of Ne charge carrier and Nh carrier in intrinsic charge carrier.
Why are the n-type and p-type semiconductors electrically neutral?
Draw the symbol of Zener diode.
Give the symbol of NPN and pnp transistor.
What is transconductance?
Draw the v-I characteristic of a Zener diode.
Write the truth table of NAND gate.
What is the order of forbidden energy gap in a conductor, insulator and semiconductor?
Which has greater mobility- Electrons or Holes? Why?
GROUP VIII
PRINCIPLE OF COMMUNICATION
Level-1
1. What are radio waves?
2. What is Antenna?
3. What is band width of signal?
4. What do you mean by transmission medium?
5. What do you mean by uplink & downlink?
6. What do you mean by communication?
7. What is the condition for a satellite to be geostationary?
8. Show diagrammatically sky wave propagation.
9. What is modulation?
10. How does Effective power radiated by an antenna depend upon wavelength?
Level-2
1 What is height of antenna if transmission frequency is 1 MHz?
2 Show diagrammatically the amplitude modulation.
3 Define guided & unguided transmission medium.
4 What do you mean by maximum line of sight distance (dm)? Write its formula?
5 Why can moon be not used as a communication satellite?
6 A tower has height of 100m. How much population is covered by the T.V broadcast if the average population
density around the tower is 1500 Km sq. (radius of the Earth 6400Km)
7 why is ground wave transmission of signal restricted to a frequency of 1500 KHz?
8 What is the significance of modulation index? An audio signal of amplitude one half the carrier amplitude is used
in amplitude modulation. Calculate modulation index?
9 What type of modulation is needed for the commercial broadcast of voice signals?
10 Why is the transmission of signals through a coaxial cable not possible for frequencies greater than 20 MHz?
11 Why is short wave band used for long distance radio broadcast?
12 Name an appropriate communication channel needed to send a signal of bandwidth 100 kHz over distance of 8
km
13 Why is FM preferred over AM for transmission of music?
14 Why modulation is needed to transmit signals?
15 State two factors by which the range of the transmission of signals by a TV tower can be increased.
16 How do we make the choice of communication channel?
17 By what factor the height of antenna must be increased in order to double the coverage range? Given radius of
earth equal to 6400 km.
18 Which of the following frequencies will be suitable for beyond-the horizon communication using sky waves?
(a) 10 kHz (b) 10 MHz (c) 1 GHz (d) 1000 GHz
19. Name the type of communication system according to the mode of communication.
20. Name the device which can represent digital data by analog signals and vice versa.
Level-3
1. With suitable diagram describe the detection of amplitude modulated wave.
2. Explain why VHF are not used for sky wave propagation.
3. If maximum value of signal and carrier waves are 4volt & 5volt respectively. Find
(i) The maximum and minimum value of modulated amplitude in volt.
(ii) Percentage of modulation
4. A transmitting antenna at the top of tower has height 32m & that of receiving antenna is 50m. What is
maximum difference b/w them for satisfactory communication in line of sight mode? (R=6400Km)
5. A radio can tune to any station in 7.5MHz to 12MHz band. What is the corresponding wave length range?
6. What is an active satellite? How is it different from a passive satellite?
7. If 2% part of 10GHz communication is used in unguided communication then how many channels can be
adjusted in this frequency range if each channel has a band width of 8 KHz?
8 Give the frequency range used in mobile signal and satellite communication.
9 Explain how will you obtain an AM wave using a square law device? Obtain the expression for the AM wave
obtained using such a device.
10 A schematic arrangement for transmitting a message signal 20 to 20 kHz is given below:
Give two drawbacks from which this arrangement suffers and draw an alternate arrangement overcoming the said
drawback.
GROUP VIII
EM WAVES
Level I
1. Write four Maxwell’s Equations & write the signification of each equation.
2. Draw labeled diagram of Hertz experimental set up. Explain how e.m. radiations are produced using this set up.
3. Write four properties of electromagnetic waves.
4. Write the expression for the velocity of e.m. waves in terms of permittivity and permeability of the medium
5. Which part of e.m. waves has
(i) lowest frequency
(ii) highest frequency
6. Draw a diagram to show transverse nature of e.m. waves.
7. Write the relation of speed of e.m. waves in
(i) free space
(ii) medium.
8. Name the Maxwell’s equation among the four which shows that the magnetic monopole does not exist.
9. Which of the following quantities are not transported along with electromagnetic waves?
(i) Energy (ii) Charge (iii) Momentum (iv) Information
Level II
1. What oscillates in e.m. waves? Are these waves longitudinal or transverse?
2. What is the ratio of speed of gamma rays and radio waves in vacuum?
3. Why can light waves travel in vacuum, whereas sound waves cannot do so?
4. Which waves are used
(i) in mobile phones
(ii) in look through fog.
(iii) in radar
(iv) in geostationary satellites
(v) To study structure a properties of atoms and molecules.
5. Write two applications each of
(i) microwaves
(ii) infrared waves
(iii) radio waves
6. What role does ozone layer play for human survival?
7. A radio can tune into any station, the 7.5 MHz to 12MHz band. What is the corresponding wavelength band?
8. How does a charge q oscillating at certain frequency produce electromagnetic waves.
9. Which of the following can act as the source of e.m. waves?
(i) A charge moving with constant velocity
(ii) A charge moving in circular orbit
(iii) An accelerated charge
(iv) A charge at rest
10. Give reason for decrease or increase in velocity of light, when it moves from air to glass and glass to air
respectively.
Level III
1. In a plane electromagnetic wave, the electric field oscillates with a frequency of 2 X 1010 per second and
amplitude of 40 V m-1.
(i) What is the wavelength of the wave?
(ii) What is the energy density due to the electric field?
[ Ans. (i) = 1.5 X 10 -2 m
(ii) ] 3 9 2 0 0 2 0 10 54 .34 / 12 / 1Jm E E U rms E
2. Why do welders wear special glass goggles or face masks with glass window?
3. A plane e.m. wave of frequency 25 MHz travels in free space along x-axis. At a particular point in space and time,
the electric vector is = 6.3 Vm-1 j. Calculate B at this point. E
[Hint: E = B.C = 2.1 X 10 -8 t ] B k
4. Suppose that the amplitude of electric field in an electromagnetic wave is
E0 = 120 N/C and its frequency is 50 MHz Determine B0, , k and .
5. Suppose that the electric field part of an electromagnetic wave in vacuum is
E = {(3.1 N/C) cos [(1.8 rad/m) y + (5.4 × 106 rad/s)t]}ˆi .
(a) What is the direction of propagation?
(b) What is the wavelength ?
(c) What is the frequency ?
(d) What is the amplitude of the magnetic field part of the wave?
(e) Write an expression for the magnetic field part of the wave.