NEET Electromagnetic Induction — Set 23

Question 1

A wheel with 5 spokes of 0.4 m each rotates at 30 rpm in a 0.7 T field. What is the induced emf?

Accepted Answer

$ \omega = 2\pi \times \frac{30}{60} = \pi \, \text{rad/s} $. $ \varepsilon = \frac{1}{2} B \omega R^2 = \frac{1}{2} \times 0.7 \times \pi \times (0.4)^2 = 0.1759 \, \text{V} \approx 0.176 \, \text{V} $.

Question 2

A solenoid of 1000 turns/m and area 0.01 m² has $ \mu_r = 2 $. What is its self-inductance? ($ \mu_0 = 4\pi \times 10^{-7} \, \text{H/m} $)

Accepted Answer

$ L = \mu_r \mu_0 n^2 A l $, assume $ l = 1 \, \text{m} $. $ L = 2 \times 4\pi \times 10^{-7} \times (1000)^2 \times 0.01 \times 1 = 0.02513 \, \text{H} \approx 0.025 \, \text{H} $.

Question 3

A coil of 130 turns and area 0.04 m² is in a field that increases from 0 to 0.05 T in 0.2 s. What is the induced emf?

Accepted Answer

$ \Delta \Phi = B A = 0.05 \times 0.04 = 0.002 \, \text{Wb} $. $ \varepsilon = N \frac{\Delta \Phi}{\Delta t} = 130 \times \frac{0.002}{0.2} = 130 \times 0.01 = 1.3 \, \text{V} $.

NEET Physics: Electromagnetic Induction — Practice Set 23

Q1. A wheel with 5 spokes of 0.4 m each rotates at 30 rpm in a 0.7 T field. What is the induced emf?

Q2. A solenoid of 1000 turns/m and area 0.01 m² has \( \mu_r = 2 \). What is its self-inductance? (\( \mu_0 = 4\pi \times 10^{-7} \, \text{H/m} \))

Q3. A coil of 130 turns and area 0.04 m² is in a field that increases from 0 to 0.05 T in 0.2 s. What is the induced emf?

Q4. In an AC generator, slip rings are used instead of a split ring commutator. What is the primary reason for this design choice?

Q5. A conducting loop is placed in a magnetic field that remains constant in magnitude and direction. No emf is induced because of what condition?

Q6. A coil of 80 turns is placed in a magnetic field that increases from 0 to 0.03 Wb/m² in 0.2 s. If the coil area is 0.05 m², what is the induced emf?

Q7. A circular loop of radius 15 cm is deformed into a straight wire in a 0.15 T field in 0.6 s. What is the induced emf?

Q8. A solenoid of 550 turns per meter and area 0.016 m² has a current drop from 7 A to 4 A in 0.3 s. What is the self-induced emf? (\( \mu_0 = 4\pi \times 10^{-7} \, \text{H/m} \))

Q9. A solenoid of 700 turns/m and area 0.008 m² has \( \mu_r = 1 \). What is its self-inductance? (\( \mu_0 = 4\pi \times 10^{-7} \, \text{H/m} \))

Q10. A coil of 120 turns and area 0.04 m² is in a 0.09 T field that drops to zero in 0.3 s. What is the induced emf?