Platinum Jubilee School & Jr.

College, Gadchiroli
First Term Exam 2023-24
Subject– Physics Marks–70 Std. XII Time –3.00 hrs.

General Instruction
(1) There are 35 questions in all. All questions are compulsory
(2) This question paper has five sections: Section A, Section B, Section C, Section D and Section
E. All the sections are compulsory.
(3) Section A contains eighteen MCQ of 1mark each, Section B contains seven questions of
two marks each,
(4) There is no overall choice. However, an internal choice has been provided in Section B, C, D
and E. You have to attempt only one of the choices in such questions.
(5) Use of calculators is not allowed.

SECTION A
1. The work done against electrostatic force gets stored in which form of energy?
a. Thermal energy b. Kinetic energy c. Potential energy d. Solar energy
2. The capacity of the parallel plate capacitor increases when
a. area of the plate is decreased
b. area of the plate is increased
c. distance between the plates increases
d. None of the option
3. Unit of conductance is __________.
a. Dyne b. Siemen c. Ohm d. Volts
4. The opposition offered by the electrolyte of the cell to the flow of current through itself is
known as ___.
a. External resistance c. Internal resistance c. Non-resistance d. None of these
5. SI unit of the magnetic field is _________.
a. Dyne b. Ohm c. Tesla d. Volt
6. Magnetic field at any point inside the straight solenoid is given as———-
a. B = μ0/nI b. B = μ0/n+I c. B = μ0n/I d. B = μ0nI
7. 1 Gauss =
a. 104 Tesla b. 10-4 Tesla c. 102 Tesla d. 10-2 Tesla
8. Lorentz force is given by the formula
a. F= q(v + B + E) b. F= q(v – B – E) c. F= q(v * B * E) d. F= q(v * B + E)
9. Which of the following states that an emf is induced whenever there is a change in the magnetic
field linked with electric circuits?
a. Lenz’s Law c. Ohm’s Law
b. Faraday’s Law of Electromagnetic Induction d. None of the above
10. Which of the following apparatus construction uses electromagnetic induction?
a. Voltmeter b. Galvanometer c. Generator d. Electric Motor
11. Which of the following waves have a maximum frequency?
a. infrared waves b. gamma rays c. microwaves d. radio waves
12. Which of the following radiations are used to treat muscle ache?
a. Microwaves b. Infrared Rays c. Ultraviolet Rays d. X-Rays
13. When the charged particles move in a combined magnetic and electric field, then the force
acting is known as _________.
a. Centripetal force b. Centrifugal force c. Lorentz force d. Orbital force
14. The concept of displacement current was introduced by _________.
a. Newton b. Ampere c. Fleming d. Maxwell
15. Magnetic field at the centre of a circular current-carrying conductor/coil is given by
μ0I μ0+I 𝐼 μ0r𝐼
a. B= 2𝑟 b. B = 2+𝑟 c. B= 2𝑟 d. B = 2
Directions: These questions consist of two statements, each printed as Assertion and Reason.
While answering these questions, you are required to choose any one of the following four
responses.
(a) Assertion is correct, reason is correct; reason is a correct explanation for assertion.
(b) Assertion is correct, reason is correct; reason is not a correct explanation for assertion
(c) Assertion is correct, reason is incorrect
(d) Assertion is incorrect, reason is correct.
16. Assertion : In series LCR resonance circuit, the impedance is equal to the ohmic resistance.
Reason: At resonance, the inductive reactance exceeds the capacitive reactance.
17. Assertion : A capacitor is connected to a direct current source. Its reactance is infinite.
Reason : Reactance of a capacitor is given by χc = 1/ωC.
18. Assertion : Average value of ac over a complete cycle is always zero.
Reason: Average value of ac is always defined over half cycle.
SECTION B
19. The instantaneous current and voltage of an a. c. circuit are given by
i = 10 sin 300 t A and V = 200 sin 300 t V. What is the power dissipation in
the circuit?
20. Define the current sensitivity of a galvanometer. Write Its S.I. unit. The
figure shows two circuits each having a galvanometer and a battery of 3
V. When the galvanometers in each arrangement do not show any
deflection, obtain the ratio R1/R2.
21. Figure shows three point charges, +2q, -q and + 3q. Two charges +2q and -q
are enclosed within a surface ‘S’. What is the electric flux due to this
configuration through the surface ‘S’
OR
Write any four properties of magnetic field.
22. Two point charges 20 x 10-6 C and -4 X 10-6 C are separated by a distance of 50 cm in air.
(i) Find the point on the line joining the charges, where the electric potential is zero.
(ii) Also find the electrostatic potential energy of the system.
23. Use Ampere’s circuital law, to obtain the expression for the magnetic field due to the current I in
a long solenoid having n number of turns per unit length.
OR
A closely wound solenoid of 2000 turns and cross sectional area 1.6 × 10-4 m2 carrying a current
of 4.0 A is suspended through its centre allowing it to turn in a horizontal plane. (i) The magnetic
moment associated with the solenoid, (ii) Magnitude and direction of the torque on the solenoid
if a horizontal magnetic field of 7.5 ×10-2 T is set up at an angle of 30° with the axis of the
solenoid.
24. (a) Define the SI unit of capacitance.
(b) Obtain the expression for the capacitance of a parallel plate capacitor.
25. An inductor of unknown value, a capacitor of 100 μF and a resistor of 10 Ω are connected in
series to a 200 V. 50 Hz a.c. source. It is found that the power factor of the circuit is unity.
Calculate the inductance of the inductor and the current amplitude.
SECTION C
26. Explain the term ‘drift velocity’ of electrons in a conductor. Hence obtain the expression for the
current through a conductor in terms of ‘drift velocity’.
27. State the underlying principle of a transformer.
How is the large-scale transmission of electric energy over long distances
done with the use of transformers?
28. The figure shows a series LCR circuit with L = 5.0 H, C = 80 μF, R = 40 Ω
connected to a variable frequency 240 V source. Calculate
(i) The angular frequency of the source which drives the circuit at
resonance.
(ii) The current at the resonating frequency. (iii) The rms potential drop
across the capacitor at resonance.
OR
2
Check that the ratio ke /G memp is dimensionless. Look up a Table of Physical Constants and
determine the value of this ratio. What does the ratio signify?
29. Using Ampere’s circuital law, obtain an expression for the magnetic field along the axis of a current
carrying solenoid of length l and having N number of turns.
OR
Draw magnetic field lines when a i) diamagnetic, ii) paramagnetic substance is placed in an
external magnetic field. Which magnetic property distinguishes this behaviour of the field lines
due to the two substances?
30. Three capacitors of capacitances 2 pF, 3 pF and 4 pF are connected in parallel.
(a) What is the total capacitance of the combination?
(b) Determine the charge on each capacitor if the combination is connected to a 100V supply.
SECTION D
31. Determine the current in each branch of the network shown in fig:
OR
Explain the two Kirchhoff’s Laws. And also justify these laws.

32. (a) Three resistors 2 Ω, 4 Ω and 5 Ω are combined in parallel. What is the
total resistance of the combination?
 (b) If the combination is connected to a battery of emf 20 V and negligible internal resistance,
determine the current through each resistor, and the total current drawn from the battery.
33. Draw a sketch showing the basic elements of an a.c. generator. State its principle and explain
briefly its working.
OR
Describe briefly, with the help of a labelled diagram, the basic elements of an a.c. generator. State
its underlying principle. Show diagrammatically how an alternating emf is generated by a loop of
wire rotating in a magnetic field. Write the expression for the instantaneous value of the emf
induced in the rotating loop.
SECTION E
34. Resistance is a measure of the opposition to current flow in an
electrical circuit. Resistance is measured in ohms. Also, Resistivity
is the electrical resistance of a conductor of unit cross-sectional
area, and unit length. A characteristic property of each material,
resistivity is useful in comparing various materials on the basis of
their ability to conduct electric currents.
1. Resistivity is independent of:
a. nature of material b. temperature
c. dimensions of material d. none of the above
2. As compared to short wires, long wires have _______ resistance.
a. More b. less c. same d. zero
3. As compared to thin wires, thick wires have _______ resistance.
a. More b. less c. same d. zero
4. The resistance of a wire depends upon:
a. cross-sectional area b. length of wire
c. wire’s nature d. all of the above
OR
A copper wire having the same size as steel wire have:
a. more resistance b. less resistance
c. same resistance d. none of the above
35. Read the following source and answer any four out of the following
questions:
Electric charge is the physical property of matter that causes it to
experience a force when placed in an electromagnetic field. There are two
types of charges positive and negative charges. Also, like charges repel
each other whereas unlike charges attract each other.
1. Charge on a body which carries 200 excess electrons is:
a.-3.2 × 10-18 C b. 3.2 × 10 18 C c. -3.2 × 10-17 C d. 3.2 × 10 -17 C
2. Charge on a body which carries 10 excess electrons is:
a.-1.6 × 10-18 C b. 1.6 × 10 -18 C c. 2.6 × 10-18 C d. 1.6 × 10-21 C
3. Mass of electron is:
a. 9.1 × 10-31 kg b. 9.1 × 10-31 g c. 1.6 × 10-19 kg d. 1.6 × 10-19 g
4. A body is positively charged, it implies that:
a. There is only a positive charge in the body.
b. There is positive as well as negative charge in the body but the positive charge is more
than negative. charge
c. There is equally positive and negative charge in the body but the positive charge lies in the
outer regions.
d. The negative charge is displaced from its position.
OR
On rubbing, when one body gets positively charged and the other negatively charged, the
electrons transferred from the positively charged body to the negatively charged body are:
a. valence electrons only c. electrons of inner shells
b. both valence electrons and electrons of the inner shell. d. none of the above