CBSE Class 12 Physics Electromagnetic Induction Worksheet Set A

CBSE Class 12 Physics Electromagnetic Induction Worksheet Set A

Question. A metal conductor of length 1 m rotates vertically about one of its ends at angular velocity 5 radians per second. If the horizontal component of earth’s magnetic field is 0.2 × 10^–4T, then the e.m.f. developed between the two ends of the conductor is
(a) 5 mV
(b) 50 μV
(c) 5 μV
(d) 50 mV

Answer: B

Question. Two identical induction coils each of inductance L are jointed in series are placed very close to each other such that the winding direction of one is exactly opposite to that of the other, what is the net inductance?
(a) L²
(b) 2 L
(c) L /2
(d) zero

Answer: D

Question. Consider the situation shown. The wire AB is sliding on fixed rails with a constant velocity. If the wire AB is replaced by semi-circular wire, the magnitude of induced e.m.f. will
(a) increase
(b) decrease
(c) remain the same
(d) increase or decrease depending on whether the semicircle buldges towards the resistance or away from it.

Answer: C

Question. A generator has an e.m.f. of 440 Volt and internal resistance of 4000 hm. Its terminals are connected to a load of 4000 ohm. The voltage across the load is
(a) 220 volt
(b) 440 volt
(c) 200 volt
(d) 400 volt

Answer: D

Question. A circular coil and a bar magnet placed nearby are made to move in the same direction. If the coil covers a distance of 1 m in 0.5. sec and the magnet a distance of 2 m in 1 sec, the induced e.m.f. produced in the coil is
(a) zero
(b) 0.5 V
(c) 1 V
(d) 2 V.

Answer: A

Question. A horizontal telegraph wire 0.5 km long running east and west in a part of a circuit whose resistance is 2.5 Ω. The wire falls to g = 10.0 m/s² and B = 2 × 10^–5 weber/ m², then the current induced in the circuit is
(a) 0.7 amp
(b) 0.04 amp
(c) 0.02 amp
(d) 0.01 amp

Answer: C

Question. Two identical coaxial circular loops carry current i each circulating in the clockwise direction. If the loops are approaching each other, then
(a) current in each loop increases
(b) current in each loop remains the same
(c) current in each loop decreases
(d) current in one-loop increases and in the other it decreases

Answer: C

Question. A coil has 200 turns and area of 70 cm2. The magnetic field perpendicular to the plane of the coil is 0.3 Wb/m² and take 0.1 sec to rotate through 180º.The value of the induced e.m.f. will be
(a) 8.4 V
(b) 84 V
(c) 42 V
(d) 4.2 V

Answer: A

Question. The inductance between A and D is
(a) 3.66 H
(b) 9 H
(c) 0.66 H
(d) 1 H

Answer: D

Question. If N is the number of turns in a coil, the value of self inductance varies as
(a) N⁰
(b) N
(c) N²
(d) N^–2

Answer: C

Question. A coil is wound on a frame of rectangular cross-section. If all the linear dimensions of the frame are increased by a factor 2 and the number of turns per unit length of the coil remains the same, self-inductance of the coil increases by a factor of
(a) 4
(b) 8
(c) 12
(d) 16

Answer: B

Question. A thin circular ring of area A is held perpendicular to a uniform magnetic field of induction B. A small cut is made in the ring and a galvanometer is connected across the ends such that the total resistance of the circuit is R. When the ring is suddenly squeezed to zero area, the charge flowing through the galvanometer is
(a) BR/A
(b) AB/A
(c) ABR
(d) B²A/R²

Answer: B

Question. The flux linked with a coil at any instant 't' is given by Φ = 10t² – 50t + 250. The induced emf at t = 3s is
(a) –190 V
(b) –10 V
(c) 10 V
(d) 190 V

Answer: B

Question. A current of 2.5 A flows through a coil of inductance 5 H. The magnetic flux linked with the coil is 
(a) 2 Wb
(b) 0.5 Wb
(c) 12.5 Wb
(d) Zero

Answer: C

Question. Two coaxial solenoids are made by winding thin insulated wire over a pipe of cross-sectional area A = 10 cm² and length = 20 cm. If one of the solenoid has 300 turns and the other 400 turns, their mutual inductance is (μ₀ = 4π × 10^–7 Tm A^–1)
(a) 2.4π × 10^–5 H
(b) 4.8π × 10^–4 H
(c) 4.8π × 10^–5 H
(d) 2.4π × 10^–4 H

Answer: D

Question. A varying current in a coil change from 10A to zero in 0.5 sec. If the average e.m.f induced in the coil is 220V, the selfinductance of the coil is
(a) 5 H
(b) 6 H
(c) 11 H
(d) 12 H

Answer: C

Question. A conducting square frame of side ‘a’ and a long staight wire carrying current I are located in the same plane as shown in the figure. The frame moves to the right with a constant velocity ‘V’. The emf induced in the frame will be proportional to 

Answer: C

Question. A conductor of length 0.4 m is moving with a speed of 7 m/s perpendicular to a magnetic field of intensity 0.9 Wb/m². The induced e.m.f. across the conductor is
(a) 1.26 V
(b) 2.52 V
(c) 5.04 V
(d) 25.2 V

Answer: B

Question. The mutual inductance between two coils depends on
(a) medium between the coils
(b) separation between the two coils
(c) orientation of the two coils
(d) All of the above

Answer: D

Question. In an inductor of self-inductance L = 2 mH, current changes with time according to relation i = t²e^–t. At what time emf is zero?
(a) 4s
(b) 3s
(c) 2s
(d) 1s

Answer: C

Question. The back e.m.f. in a d.c. motor is maximum, when
(a) the motor has picked up max speed
(b) the motor has just started moving
(c) the speed of motor is still on the increase
(d) the motor has just been switched off

Answer: A

Question. Two coils have a mutual inductance 0.005H. The current changes in first coil according to equation I = I₀ sin ωt where I₀ = 10A and w = 100p radian/sec. The max. value of e.m.f. in second coil is
(a) 2π
(b) 5π
(c) π
(d) 4π

Answer: B

Question. A thin semicircular conducting ring (PQR) of radius ‘r’ is falling with its plane vertical in a horizontal magnetic field B, as shown in figure. The potential difference developed across the ring when its speed is v, is : 

(a) Zero
(b) Bvπr² /2 and P is at higher potnetial
(c) πrBv and R is at higher potnetial
(d) 2rBv and R is at higher potential

Answer: D
 

              Very Short Answer

Q1)       What happens when the magnet is pulled away from the coil?

Q2)       What is SI unit of magnetic flux??

Q3)       Define electromagnetic induction?

Q4)       What is motional electromotive force?

Q5)       Who gave the experiments of the electromagnetic induction?

              Short Answer

Q6)       Difference between magnetism and electromagnetism?

Q7)       What do you meant by Faraday’s law of induction?

Q8)       What do you mean by the magnetic flux?

Q9)       What do you mean by the electromagnetic damping?

Q10)     Why magnetic flux is a scalar quantity?

              Long Answer

Q11)     Explain the eddy current and what its advantages?

Q12)     Explain inductance?

Q13)     Write short note on Len’s law?

Q14)     State the difference between AC generator and Dc generator?

Q15)     State the difference between magnetism and gravity?