NEET Electromagnetic Induction — Set 21

Question 1

A coil with $ L = 0.3 \, \text{H} $ has its current increased from 0 to 6 A in 0.6 s. What is the energy stored?

Accepted Answer

$ W = \frac{1}{2} L I^2 = \frac{1}{2} \times 0.3 \times (6)^2 = 0.15 \times 36 = 5.4 \, \text{J} $.

Question 2

A circular loop of radius 10 cm is deformed into a straight wire in a 0.1 T field. If the flux change occurs in 0.2 s, what is the induced emf?

Accepted Answer

Initial flux: $ \Phi = B A = 0.1 \times \pi \times (0.1)^2 = 0.00314 \, \text{Wb} $. Final flux = 0. $ \varepsilon = \frac{\Delta \Phi}{\Delta t} = \frac{0.00314}{0.2} = 0.0157 \, \text{V} \approx 0.016 \, \text{V} $.

Question 3

A magnet is dropped through a vertical copper tube. The magnet’s fall is slower than expected due to what effect?

Accepted Answer

The falling magnet induces currents in the copper tube, which create a magnetic field opposing the magnet’s motion, slowing its fall. This is an application of Lenz’s law.

NEET Physics: Electromagnetic Induction — Practice Set 21

Q1. A coil with \( L = 0.3 \, \text{H} \) has its current increased from 0 to 6 A in 0.6 s. What is the energy stored?

Q2. A circular loop of radius 10 cm is deformed into a straight wire in a 0.1 T field. If the flux change occurs in 0.2 s, what is the induced emf?

Q3. A magnet is dropped through a vertical copper tube. The magnet’s fall is slower than expected due to what effect?

Q4. A magnet is moved towards a coil, inducing a current. If the magnet’s speed increases, what happens to the induced current?

Q5. A circular coil of radius 8 cm and 150 turns rotates at 25 rad/s in a 0.06 T field. What is the maximum emf induced?

Q6. A coil is wound tightly around a core material. If the current through it changes rapidly, the induced emf opposing this change is an example of which phenomenon?

Q7. A solenoid of 400 turns and length 0.5 m induces an emf of 0.8 V in a nearby coil when its current changes from 2 A to 4 A in 0.2 s. What is the mutual inductance?

Q8. A coil of 130 turns and area 0.08 m² is in a 0.12 T field that drops to zero in 0.4 s. What is the induced emf?

Q9. A coil with \( L = 0.6 \, \text{H} \) has its current increased from 0 to 5 A in 0.5 s. What is the energy stored?

Q10. A solenoid with mutual inductance 0.2 H has a current change of 5 A/s in the primary coil. What is the induced emf in the secondary coil?