# Class 12 Physics Sample Paper Term 1 Set B

Please refer to Class 12 Physics Sample Paper Term 1 Set B with solutions below. The following CBSE Sample Paper for Class 12 Physics has been prepared as per the latest pattern and examination guidelines issued by CBSE. By practicing the Physics Sample Paper for Class 12 students will be able to improve their understanding of the subject and get more marks.

## CBSE Class 12 PhysicsSample Paper for Term 1

Section – A

This section consists of 25 multiple choice questions with overall choice to attempt any 20 questions. In case more than desirable number of questions are attempted, ONLY first 20 will be considered for evaluation.

Q. 1. An electric dipole has the magnitude of its charge as q and its dipole moment is p. It is placed in a uniform electric field E. If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively :
(A) 2q⋅E and minimum
(B) q⋅E and p⋅E
(C) Zero and minimum
(D) q⋅E and maximum

C

Q. 2. If identical charges (−q) are placed at each corner of a cube of side b, then electric potential energy of charge (+q) which is placed at centre of the cube will be :
(A) 8√2q2/4πε0b
(B) − 8√2q2/πε0b
(C) − 4√2q2/πε0b
(D) − 4q2/√3πε0b

D

Q. 3. The electric intensity due to a dipole of length 10 cm and having a charge of 500 μC, at a point on the axis at a distance 20 cm from one of the charges in air, is :
(A) 6.25×107 N/C
(B) 9.28×107 N/C
(C) 13.1×1111 N/C
(D) 20.5×107 N/C

A

Q. 4. A point Q lies on the perpendicular bisector of an electrical dipole of dipole moment p. If the distance of Q from the dipole is r (much larger than the size of the dipole), then electric field at Q is proportional to :
(A) p−1 and r−2
(B) p and r−2
(C) p−1 and r−2
(D) p and r−3

D

Q. 5. A capacitor is charged by a battery. The battery is removed and another identical uncharged capacitor is connected in parallel. The total electrostatic energy of resulting system :
(A) decreases by a factor of 2
(B) remains the same
(C) increases by a factor of 2
(D) increases by a factor of 4

A

Q. 6. A parallel plate air capacitor of capacitance C is connected to a cell of emf V and then disconnected from it. A dielectric slab of dielectric constant K, which can just fill the air gap of the capacitor, is now inserted in it. Which of the following is incorrect?
(A) The change in energy stored is 1/2CV2 (1/K – 1)
(B) The charge on the capacitor is not conserved
(C) The potential difference between the plates decreases K times.
(D) The energy stored in the capacitor decreases K times.

B

Q. 7. A conducting sphere of radius R is given a charge Q. The electric potential and the electric field at the centre of the sphere respectively are :
(A) Zero and Q/4πεoR2
(B) Q/4πεoR and Zero
(C) Q/4πεoR and Q/4πεoR2
(D) Both are zero.

B

Q. 8. In the given figure, equivalent resistance between A and B will be :

(A) 14/3 Ω
(B) 3/14 Ω
(C) 9/14 Ω
(D) 14/9 Ω

A

Q. 9. An electron moving in a circular orbit of radius r makes n rotations per second. The magnetic field produced at the centre has magnitude :
(A) Zero
(B) μ0n2e/r
(C) μ ne/2r
(D) μ0ne/2πr

C

Q. 10. Under the influence of a uniform magnetic field, a charged particle moves with constant speed V in a circle of radius R. The time period of rotation of the particle :
(A) depends on R and not on V
(B) is independent of both V and R
(C) depends on both V and R
(D) depends on V and not on R

B

Q. 11. A straight wire of diameter 0.5 mm carrying a current of 1A is replaced by another wire of 1 mm diameter carrying same current. The strength of magnetic field far away is :
(A) twice the earlier value
(B) same as earlier value
(C) one-half of the earlier value
(D) one-quarter of the earlier value

B

Q. 12. The average e.m.f. induced in a coil in which the current changes from 2A to 4A in 0.05 second is 8 volt. What is the self-inductance of the coil?
(A) 0.1 H
(B) 0.2 H
(C) 0.4 H
(D) 0.8 H

B

Q. 13. A step-up transformer operates on a 230 V line and supplies current of 2 A to a load. The ratio of the primary and secondary windings is 1 : 25. The current in the primary coil is :
(A) 15 A
(B) 50 A
(C) 25 A
(D) 12.5 A

B

Q. 14. An ac circuit consists of an inductor of inductance 0.5 H and a capacitor of capacitance 8 mF in series. The current in the circuit is maximum when the angular frequency of ac source is :

A

Q. 15. A cylindrical bar magnet of radius 0.8 cm is dropped through a metallic pipe of inner radius 1 cm.
It takes more time to come down than it takes for a similar un-magnetized cylindrical iron bar dropped through the metallic pipe. This happens due to
(A) Friction
(B) Electrostatic charge developed on the inner wall of the pipe
(C) Generation of eddy current
(D) Buoyancy

C

Q. 16. Current in a circuit falls from 5.0 A to 0.0 A in 0.1 s. If an average emf of 200 V induced, the selfinductance of the circuit is
(A) 4 H
(B) 4 mH
(C) 40 mH
(D) 40 H

A

Q. 17. The polarity developed at the right end of 1st coil will be _______ pole and the polarity developed at the left end of the 2nd coil will be _______ pole.

(A) South, North
(B) North, South
(C) North, North
(D) South, South

D

Q. 18. 1 Henry = volt-sec/ampere
(A) 10
(B) 1
(C) 103
(D) 10–3

B

Q. 19. The Q value of a series LCR circuit with L = 2.0 H, C = 32 μF and R = 10 Ω is
(A) 25
(B) 0.4 × 10–3
(D) 2500

A

Q. 20. A device ‘X’ is connected to an a.c. source. The variation of voltage, current and power in one complete cycle is shown in Figure.

Curve _______ shows power consumption over a full cycle and the device X is a _________ .
(A) A, capacitor
(B) A, inductor
(C) Either (A) or (B)
(D) B, capacitor

C

Q. 21. A device X is connected across an ac source of voltage V = Vo sin wt. The current through X is given as I = Io sin (wt ± π/2 ). Which of the following graphs show the correct variation of voltage and current with time over one cycle of ac, for X.

A

Q. 22. Which of the following transformer winding is correct?

C

Q. 23. A silver wire has a resistance of 2.1 Ω at 27.5 °C, and a resistance of 2.7 Ω at 100 °C. The temperature coefficient of resistivity of silver is
(A) 0.0039°C–1
(B) 0.039°C–1
(C) 0.39°C–1
(D) None of the above

A

Q. 24. Given the resistances of 1 Ω, 2 Ω, 3 Ω. How will these be combined to get an equivalent resistance of 11/3 Ω?
(A) 1 Ω and 2 Ω in parallel and with this combination 3 Ω in series.
(B) 3 Ω and 2 Ω in parallel and with this combination 1 Ω in series.
(C) 1 Ω and 3 Ω in parallel and with this combination 2 Ω in series.
(D) all three resistors in parallel

A

Q. 25. AB is a potentiometer wire (Figure). If the value of R is increased, balance point J

(A) shift towards A
(B) shift towards B
(C) Remains in same position
(D) will be missing.

B

Section – B

This section consists of 24 multiple choice questions with overall choice to attempt any 20 questions. In case more than desirable number of questions are attempted, ONLY first 20 will be considered for evaluation.

Q. 26. If a unit positive charge is taken from one point to another over an equipotential surface, then :
(A) Work is done on the charge
(B) Work is done by the charge
(C) Work done is constant
(D) No work is done

D

Q. 27. The electric field inside a spherical shell of uniform surface charge density is :
(A) Zero
(B) Constant, less than zero
(C) Directly proportional to the distance from the centre
(D) None of the above

A

Q. 28. The distance between the two charges +q and −q of a dipole is r. On the axial line at a distance d from the centre of dipole, the intensity is proportional to :
(A) q/d2
(B) qr/d2
(C) q/d3
(D) qr/d3

D

Q. 29. 2μF capacitance has potential difference across its two terminals 200 volts. It is disconnected from battery and then another uncharged capacitance is connected in parallel to it, then P.D. becomes  20 volts. Then the capacity of another capacitance will be :
(A) 2 μF
(B) 4 μF
(C) 18 μF
(D) 10 μF

C

Q. 30. A charge Q is placed at the corner of a cube. The electric flux through all the six faces of the cube is :
(A) Q/3 ε0
(B) Q/6 ε0
(C) Q/8 ε0
(D) Q/ε0

D

Q. 31. The capacity of a parallel plate capacitor with no dielectric substance but with a separation of 0.4 cm is 2 μF. The separation is reduced to half and it is filled with a dielectric substance of value 2.8. The final capacity of the capacitor is :
(A) 11.2 μF
(B) 15.6 μF
(C) 19.2 μF
(D) 22.4 μF

A

Q. 32. A short bar magnet of magnetic moment 1 J/T is placed with its axis at 60° to a uniform magnetic field of 0.2 T. Calculate the magnitude of the torque experience.
(A) 3 × 10-1 Nm
(B) 3 × 10-2 Nm
(C) 3 × 10-2 Nm
(D) 3 × 10-1 Nm

D

Q. 33. In the adjoining circuit, the e.m.f. of the cell is 2 volt and the internal resistance is negligible. The resistance of the voltmeter is 80 ohm. The reading of the voltmeter will be :

(A) 0.80 volt
(B) 1.60 volt
(C) 1.33 volt
(D) 2.00 volt

C

Q. 34. Through two parallel wires A and B, 10A and 2A of currents are passed respectively in opposite directions. If the wire A is infinitely long and the length of the wire B is 2 m, the force on the conductor B, which is situated at 10 cm distance from A will be :
(A) 8 × 10−5 N
(B) 4 × 10−7 N
(C) 4 × 10−5 N
(D) 4π × 10−7 N

A

Q. 35. If a long hollow copper pipe carries a current, then magnetic field is produced:
(A) inside the pipe only
(B) outside the pipe only
(C) both inside and outside the pipe
(D) no where

B

Q. 36. If the current is halved in a coil, then the energy stored is how much times the previous value?
(A) 1/2
(B) 1/4
(C) 2
(D) 4

B

Q. 37. In a circuit L, C and R are connected in series with an alternating voltage source of frequency f. The current leads the voltage by 45°. The value of C is :
(A) 1/2πf(2πfL+R)
(B) 1/πf(2πfL+R)
(C) 1/2πf(2πfL−R)
(D) 1/πf(2πfL−R)

A

Q. 38. The natural frequency of a L-C circuit is equal to :

B

Q. 39. An ac source is connected to a resistive circuits. Which of the following is true?
(A) Current leads the voltage and both are in same phase
(B) Current lags behind the voltage and both are in same phase
(C) Current and voltage are in same phase
(D) Any of the above may be true depending upon the value of resistance

C

Q. 40. What will be the direction of induced current when the current in the vertical wire is reducing at a steady rate?

(A) anti-clockwise
(B) Clockwise
(C) No current will be induced
(D) None of the above

C

Q. 41. Given the resistances of 1 Ω, 2 Ω, 3 Ω. How will these be combined to get an equivalent resistance of 11/5Ω?
(A) 1Ω and 2Ω in parallel and with this combination 3Ω in series.
(B) 3Ω and 2Ω in parallel and with this combination 1Ω in series.
(C) 1Ω and 3Ω in parallel and with this combination 2Ω in series.
(D) all three resistors in parallel

B

Q. 42. Three capacitors each of capacitance 9 pF are connected in series and then connected to a 120 V supply.
The total capacitance of the combination is ________ and the potential difference across each capacitor is ________ .
(A) 27pF, 120V
(B) 3 pF, 40V
(C) 27pF, 40V
(D) 3pF, 120V

B

Q. 43. Capacitance of a single conductor means
(A) When connected to a supply one side of the conductor will be positively charged, other side will be negatively charged.
(B) It is a parallel plate capacitor with two plates coinciding with each other
(C) It is a parallel plate capacitor. One plate is the conductor and the other plate is at infinite distance.
(D) None of the above.

C

Q. 44. An arbitrary surface encloses a dipole. Electric flux through this surface is
(A) 0
(B) ∞
(C) Depends on the surface enclosing the dipole.
(D) Depends on the dipole moment

A

Given below are two statements labelled as Assertion (A) and Reason (R)

Directions: In the following questions, a statement of Assertion (A) and is followed by a statement of Reason (R). Mark the correct choice as:
(A) Both Assertion (A) and Reason (R) are true, and Reason(R) is the correct explanation of (A).
(B) Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of Assertion (A).
(C) Assertion (A) is true, but Reason (R) is false.
(D) Assertion (A) is false, but Reason (R) is true.

Q. 45. Assertion (A): In a cavity in a conductor, the electric field is zero.
Reason (R): Charges in a conductor reside only at its surface.

A

Q. 46. Assertion (A): Capacity of a conductor is independent on the amount of charge on it.
Reason (R): Capacitance depends on the dielectric constant of surrounding medium, shape and size of the conductor.

A

Q. 47. Assertion (A): Galvanometer to ammeter conversion takes place by connecting a low value resistance in parallel with it.
Reason (R): The low value resistance increases the effective resistance and protects the galvanometer.

C

Q. 48. Assertion (A): Self inductance may be called the inertia of electricity.
Reason (R): Due to self inductance, opposing induced e.m.f. is generated in a coil as a result of change in current or magnetic flux linked with the coil.

B

Q. 49. Assertion (A): A transformer does not work on DC.
Reason (R): DC neither change direction nor magnitude.

A

Section – C

This section consists of 6 multiple choice questions with an overall choice to attempt any 5. In case more than desirable number of questions are attempted, ONLY first 5 will be considered for evaluation.

Q. 50. Five charges, q each are placed at the corners of a regular pentagon of side ‘a’. Electric field at the centre of the pentagon is

(A) q/4πε0r2
(B) 5q/4πε0r2
(C) 0
(D) 5q/4πε0r2

C

Q. 51. Figure shows the electric field lines around three-point charges A, B and C.

(A) A and B are positive, C is negative
(B) A and C are positive, B is negative
(C) B is positive, A and C are negative
(D) A is positive, B and C are negative.

B

CASE STUDY

Read the following text and answer the following questions on the basis of the same:
At power plant, a transformer increases the voltage of generated power by thousands of volts so that it can be sent of long distances through high-voltage transmission power lines. Transmission lines are bundles of wires that carry electric power from power plants to distant substations. At substations, transformers lower the voltage of incoming power to make it acceptable for highvolume delivery to nearby end-users.
Electricity is sent at extremely high voltage because it limits so-called line losses. Very good conductors of electricity also offer some resistance and this resistance becomes  considerable over long distances causing considerable loss.

At generating station, normally voltage is stepped up to around thousands of volts. Power losses increase with the square of current. Therefore, keeping voltage high current becomes low and the loss is minimized.
Another option of minimizing loss is the use of wires of super-conducting material. Super-conducting materials are capable of conducting without resistance, they must be kept extremely cold, nearly absolute zero, and this requirement makes standard super-conducting materials impractical to use.
However, recent advances in super-conducting materials have decreased cooling requirement.
In Germany recently 1 km super-conducting cable have been installed connecting the generating station and the destination. It has eliminated the line loss and the cable is capable of sending five times more electricity than conventional cable. Using super-conducting cables Germany has also get rid of the need of costly transformers.
Transformers generate waste heat when they are in operation and oil is the coolant of choice.
It transfers the heat through convection to the transformer housing, which has cooling fins or radiators similar to heat exchangers on the outside.
Flush point is a very important parameter of transformer oil. Flashpoint of an oil is the temperature at which the oil ignites spontaneously. This must be as high as possible (not less than 160° C from the point of safety).
Fire point is the temperature at which the oil flashes and continuously burns. This must be very high for the chosen oil (not less than 200° C).

Q. 52. Which of the following statement is true for long distance transmission of electricity?
(A) Step-down transformer is used at generating station and step-up transformer is used at destination substation.
(B) Step-down transformers are used at generating station and destination substation.
(C) Step-up transformers are used at generating station and destination substation.
(D) None of the above

D

Q. 53. Super-conducting transmission line has the following advantages:
(A) Resistance being zero, there is no I2R loss.
(B) There is no requirement of costly step-up and step-down transformers.
(C) Cable is capable of sending more electricity.
(D) All of the above

D

Q. 54. Why does stepping up voltages reduce power loss?
(A) Since resistance of conductor decreases with increase of voltage
(B) Since current decreases with increase of voltage
(C) Both of the above
(D) None of the above