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KENDRIY VIDYALAY NEW CANTT,ALLAHABAD,CLASS XII-2016-17
PRE-BOARD EXAM PHYSICS
Note:→1.Q Nos.1-5 carry 1 mark each.
2. Q Nos6-10 carry 2 marks each.
3. QNos.11-22 carry 3 marks each.
4. Q Nos.23 is value-based question of 4 marks.
5. Q Nos,24-26 carry 5 marks each.
6. All questions are compulsory and answers must have proper keywords and genuine length of answers too as
per marks allotted.
7. Use of log and trigonometric tables is allowed wherever needed.
1. Why direction of electric field lines due to +ve charge is taken outward and that due to –ve charge taken inward?
2. Explain cause of instantaneous electric current in an electric circuit.
3. Draw magnetic lines pattern when diamagnetic, paramagnetic and ferromagnetic materials are kept in a uniform
field distribution.
4. What is main difference between characteristic X-rays and gamma rays?5.Show graphically characteristics of LED
and zener diode.
6. The resistance of tungsten filament at 150oC is 133 ohm. What will be resistance at500oC.coefficient of resistance
change with temperature is 0.0045peroC.
OR
6. What series resistance must be used to charge series battery of 6 lead accumulators each of emf2V and internal
resistance 0.50 ohm.
7. Differentiate ac and dc generator.
8. State laws of photoelectric emission, and explain Einstein phototoelectric effect theory.
9.Explain Davisson Germer experiment and its significance.
10. Distinguish working of unbiased and forward biased p-n junction diode.
11. State Gauss’s theorem and prove it.
12. With the help of labelled circuit diagram explain use of npn transistor as CE amplifier.
13. State Biot-Savart law and also draw diagram only showing working of cyclotron.
14. Distinguish (a) charge and mass
(b) capacitor with dielectric slab and that with conductor slab.
OR
14. Find amount of work done in rotating an electric dipole with moment 3.3x10-8Cm. From its stable equilibrium
position to maximum unstable position in a uniform electric field of intensity 104N/C.
Distinguish E due to electric dipole along axial and equatorial axial direction variation with distance i.e.r.
15.(A)220 V ac is more dangerous than 220V dc.why?
(B)How does one understand motional emf by invoking Lorentz force acting on free charge carriers of a conductor?
(C)Deduce relation between relative permeability and susceptibility for magnetisation.
(D)What is formula for current through tangent galvanometer and deflection in magnetometer. Which law it follows.
16.What are isogonic lines.
A magnetic needle free to rotate in a vertical plane orients itself with axis vertical to a certain place on earth.
(a)what is value of H
(b)angle of dip
at this place.
17.A copper wire with resistance 0.01 ohm/m is used to wind a 400 turn solenoid of radius 1 cm and length 20 cm.
Find emf of battery which can be used to produce magnetic field of 10-2T NEAR CENTRE OF COIL.
How does a velocity selector work? Introducing change in intervening medium will bring about what change in it ?
18.WHAT is significance of maxwell’s equations?
Conduction and displacement current are individually discontinuous but their sum is continuous. Explain?
19.Draw ray diagram for astronomical telescope in normal adjustment and also with adjustment for image to be
formed at least distance of distinct vision.
Distinguish microscope and telescope.
20.How does fringe width in young’s double slit experiment change when slit separation is tripled?
YELLOW LIGHT IS USED IN SINGLE SLIT DIFFRACTION THROUGH 0.6MM SLIT.IF LIGHT IS REPLACED BY X-RAYS
how observation pattern
changes?
Brewsters law and explain Brewster angle.
21.What is impact parameter.?
Show its effectivity on deflection suffered by alpha particles as observed in Rutherford’s experiment.
Calculate speed of electron in innermost orbit of H-atom as deduced by Bohr’s theory.
22.A spectrum of a star in a spectrometer shows wavelength of some lines as
824AO,970AO,1120AO,2504AO,5173AO,6100AO.
Which of these can’t belong to H-atom spectrum.
What will be ground state and nth state momentum for the electron in H-atom.
23.Anuj’s mother has constant headache diagnosed as tumour. She was avoiding treatment due to financial
constraints. Anuj cancelled his abroad visit and utilised the related money for treatment and care for his mother.
(a)What values were displayed by Anuj and his mother?
(b)state curie’s law and radioactivity decay law.
(C)How alpha ,beta rays are emitted from any radioactive substance.
(d)What are characteristics of nuclear forces?
24(a).Deduce balanced Wheatstone condition.
(b)What is reading in ammeter x and z of shown circuit
(c)WHAT IS RESISTANCE of carbon resistors having coloured strips with order yellow, brown, golden and grey.
(d)on what factors sensitivity of a voltmeter and ammeter depend?
(e)A parallel plate is to be designed with a voltage rating of 1kV using a material of dielectric constant 3 and dielectric
strength 107V/m. For safety we would like the field never to exceed say 10% of dielectric strength. What will be
minimum area of plates required for 50pF capacitor.
25.(a)Why electric potential of earth is taken to be zero?
(b)A coil of resistance 300 ohm and inductance 1H are connected across an alternating ac voltage of frequency
300/2∏ Hz. Calculate phase difference between voltage and current in the circuit.
(c)How transformers are useful for long distance electric power transmissions.
(d)Define mean value and rms value of an ac voltage. Distinguish resistance, reactance and impedance.
26.(a)A concave mirror of 10cm is placed at a distance of 35cm from the wall. How far from the wall should an object
be placed to get image on the wall?
(b)Derive lens-maker’s formula.
(c)A diver under water look obliquely to a fisherman standing on the bank of the lake. Would the fisherman look
taller or smaller than what he actually is?
(d)What are different ways polarisation state of an unpolarised light undergoes changes?
OR
(a)find output for shown input signals fed to shown each of the gates.
(b)Why four satellites are needed for finding position accurately by GPS system?
(c)Find dynamic output resistance of the transistor whose characteristics are shown.
(d)Draw block diagram of AM wave transmitter.
(e)em=5(1+0.6cos6280t)sin(211x104t)volts. Find EMIN, ,EMAX, frequency contained in AM wave, Amplitudes of the
components.
(f) what is meant by protocol, TCP, IP, LAN, e-ticketing, MTSO, TCO?