Download q1 q2 1/r V TEST – XII ( Physics ) 1 r

PAVITRA GUPTA 9312281591
PAVITRA GUPTA 9312281591
TEST – XII ( Physics )
Electrostatics; Current Electricity; Magnetism; EMI
M.M. 35
Time : 1hour 30min
Q.1 & Q.3 carry 1 mark each.
Q.4 to Q.8 carry 2 marks each.
Q.9 to Q.12 carry 3 marks each.
Q. 13 & Q.14 carry 5 marks each.
Q.1
Draw a diagram to depict the behaviour of magnetic field lines near a ‘bar’ of copper.
Q.2
Plot a graph showing variation of the net impedance of the series combination of a resistor and a
capacitor as a function of the angular frequency of the applied voltage.
Q.3
The I-V characteristics of a resistor are
observed to deviate from a straight line
I
for higher values of current
as shown below. Why?
V
Q.4
Explain how the average velocity of free electrons in a metal at constant temperature, in an electric
field, remain constant even though the electrons are being constantly accelerated by this electric field?
Q.5
(a) Calculate the electric potential at a point X due to a point charge 0.5 µC located at 10 cm from it.
(b) Also calculate the work done in bringing a charge 3 nC from infinity to the point X.
Q.6
Calculate the equivalent capacitance between
A
9µ
µC
points A and B in the given figure. If a battery
3µ
µC
of 3 V is connected across A and B, find the
B
6µ
µC
potential difference across 3 µF capacitor.
Q.7
The two graphs drawn here, show the variation
q1
of electrostatic potential (V) with 1 for two point
r
V
charges q1 and q2.
1/r
( r being distance of the field point from the point charge )
(i) What are the signs of the two charges?
(ii) Which of the two charges has a larger magnitude and why?
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q2
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Q.8
PAVITRA GUPTA 9312281591
Two resistors connected in parallel across a 100 V supply draw 10 A current from the supply. If the
power dissipation in one resistor is 600 W, find:
(i) power dissipation in other resistor
Q.9
(ii) resistance of the other resistor.
A charge q moving in a straight line is accelerated by a potential difference of V. It enters a uniform
magnetic field B perpendicular to its path. Deduce an expression for the radius of the circular path in
which it travels, in terms of V.
Q.10
For the potentiometer shown in the figure, points
X and Y represent two terminals of an unknown emf E.
A
B
A student observed that when jockey is moved from
A and to B , the deflection remains in the same direction.
G
E
X
Y
What are the two possible faults in this circuit?
If the galvanometer deflection at B is: (i) more than that at A (ii) less than that at A,
which of the two faults, listed by you, would be there in the circuit? Give reasons in support of your
answers.
Q.11
Three students X, Y, and Z performed an experiment
I
for studying the variation of alternating currents with
X
angular frequency (ω) in a series LCR circuit and obtained
the graphs shown below. They all used a.c. sources of the
Y
same r.m.s. value and inductances of the same value.
What can we (qualitatively) conclude about the
Z
(i) capacitance value (ii) resistance values
used by them?
In which case will the quality factor be maximum?
ω0
ω
What can we conclude about nature of the
impedance of the set up at frequency ωo?
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Q.12
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State Gauss’ theorem in electrostatics. Use it to derive an expression for electric field intensity at a
point due to a uniformly distributed line charge of linear charge density λ.
Q.13
The given graphs (a) and (b) represent the variation of opposition offered by the circuit element to a.c.,
Opposition
to current
Opposition
to current
with frequency of applied emf. Identify the circuit element corresponding to each graph.
frequency
frequency
(a)
(b)
A circuit is set up by L = 100 mH, C = 5 µF and R = 100 Ω in series. An a.c. source of emf 150 2 V,
500 Hz is applied to it. Calculate the impedance.
π
What is the power dissipated in (i) resistor (ii) capacitor (iii) inductor (iv) complete circuit?
Q.14
(a) Draw the labelled diagram of moving coil galvanometer. Prove that in a radial magnetic field, the
deflection of the coil is directly proportional to the current flowing in the coil.
(b) A galvanometer can be converted into a voltmeter to measure up to
(i) ‘V’ volts by connecting a resistance R1 in series with coil.
(ii) ‘V/2’ volts by connecting a resistance R2 in series with its coil.
Find the resistance (R), in terms of R1 and R2 required to convert it into a voltmeter that can read up to
‘2V’ volts.
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