NEET Electromagnetic Induction — Set 16

Question 1

A coil of 90 turns and area 0.03 m² is in a field that increases from 0 to 0.06 T in 0.3 s. What is the induced emf?

Accepted Answer

$ \Delta \Phi = B A = 0.06 \times 0.03 = 0.0018 \, \text{Wb} $. $ \varepsilon = N \frac{\Delta \Phi}{\Delta t} = 90 \times \frac{0.0018}{0.3} = 90 \times 0.006 = 0.54 \, \text{V} $.

Question 2

A coil is placed in a magnetic field that increases in strength. The energy stored in the coil’s magnetic field comes from what source?

Accepted Answer

The energy stored ($ \frac{1}{2} L I^2 $) comes from the work done by the external source (e.g., a battery) against the back emf to establish the current.

Question 3

A solenoid of 250 turns and length 0.8 m induces an emf of 0.75 V in a nearby coil when its current changes from 0 to 2.5 A in 0.25 s. What is the mutual inductance?

Accepted Answer

$ \varepsilon = M \frac{\Delta I}{\Delta t} $. $ \Delta I = 2.5 - 0 = 2.5 \, \text{A} $, $ \Delta t = 0.25 \, \text{s} $. $ M = \frac{\varepsilon}{\frac{\Delta I}{\Delta t}} = \frac{0.75}{\frac{2.5}{0.25}} = \frac{0.75}{10} = 0.075 \, \text{H} $.

NEET Physics: Electromagnetic Induction — Practice Set 16

Q1. A coil of 90 turns and area 0.03 m² is in a field that increases from 0 to 0.06 T in 0.3 s. What is the induced emf?

Q2. A coil is placed in a magnetic field that increases in strength. The energy stored in the coil’s magnetic field comes from what source?

Q3. A solenoid of 250 turns and length 0.8 m induces an emf of 0.75 V in a nearby coil when its current changes from 0 to 2.5 A in 0.25 s. What is the mutual inductance?

Q4. A coil of self-inductance 0.8 H has its current decreased from 6 A to 3 A in 0.2 s. What is the magnitude of the induced emf?

Q5. A loop of 0.45 m × 0.2 m moves out of a 0.6 T field at 1.5 m/s along its longer side. How long does the emf last?

Q6. A rectangular loop of sides 40 cm and 20 cm moves out of a 0.9 T field at 1 m/s perpendicular to the longer side. What is the motional emf?

Q7. A coil of 220 turns rotates at 70 rad/s in a 0.05 T field. If the area is 0.025 m², what is the maximum emf?

Q8. A solenoid of 900 turns/m and area 0.015 m² has \( \mu_r = 2 \). What is its self-inductance? (\( \mu_0 = 4\pi \times 10^{-7} \, \text{H/m} \))

Q9. A square loop of side 18 cm rotates at 10 rad/s in a 0.25 T field. What is the maximum emf induced?

Q10. A circular loop of radius 11 cm is deformed into a straight wire in a 0.2 T field in 0.5 s. What is the induced emf?