Electromagnetic Induction and Alternating Currents MCQs
1. How to increase the energy stored in an inductor by four times?
(a) By doubling the current
(b) This is not possible
(c) By doubling the inductance
Answer: (a) By doubling the current
2. Consider an inductor whose linear dimensions are tripled and the total number of turns per unit length is kept constant, what happens to the self-inductance?
(a) 9 times
(b) 3 times
(c) 27 times
Answer: (b) 3 times
3. Lenz law is based on which of the following conservation>
(a) Charge
(b) Mass
(c) Momentum
(d) Energy
Answer: (d) Energy
4. What will be the acceleration of the falling bar magnet which passes through the ring such that the ring is held horizontally and the bar magnet is dropped along the axis of the ring?
(a) It depends on the diameter of the ring and the length of the magnet
(b) It is equal due to gravity
(c) It is less than due to gravity
(d) It is more than due to gravity
Answer: (c) It is less than due to gravity
5. What is the need for laminating the core of a transformer?
(a) To reduce the resistance in the winding
(b) To reduce the eddy currents
(c) To reduce the hysteresis
(d) None of the above
Answer: (b) To reduce the eddy currents
6. A wire loop is rotated in a magnetic field such that the frequency of change of direction of the induced emf is
(a) Six times per revolution
(b) Four times per revolution
(c) Twice per revolution
(d) Once per revolution
Answer: (c) Twice per revolution
7. Which of the following is the equivalent quantity of mass in electricity?
(a) Current
(b) Charge
(c) Potential
(d) Inductance
Answer: (d) Inductance
8. What is the unit of inductance?
(a) Volt/ampere
(b) Joule/ampere
(c) Volt-ampere/sec
(d) Volt-sec/ampere
Answer: (d) Volt-sec/ampere
9. What is the angle made by the plane of eddy currents with the plane of magnetic lines of force?
(a) 0°
(b) 40°
(c) 90°
(d) 180°
Answer: (c) 90°
