Electromagnetic Induction — Practice

Question 1

A 0.1 m^2 loop perpendicular to a 0.5 T field has the field reduced to zero in 0.01 s. Find the induced emf.

Accepted Answer

emf = -dPhi/dt = -(0 - 0.5 x 0.1)/0.01 = 5 V.

Question 2

A solenoid of length 0.5 m, area 4e-4 m^2, and 1000 turns. Find its self-inductance.

Accepted Answer

L = mu0 N^2 A/l = 4 pi e-7 x (1000)^2 x 4e-4 / 0.5 approximately 1e-3 H = 1 mH.

Question 3

A 10 mH inductor's current changes from 5 A to 1 A in 0.02 s. Find the induced emf.

Accepted Answer

emf = -L dI/dt = -10e-3 x (1 - 5)/0.02 = 2 V.

Question 4

An AC generator has 200 turns, area 0.05 m^2, field 0.2 T, rotating at 50 rad/s. Find peak and rms emf.

Accepted Answer

Peak = NBA omega = 200 x 0.2 x 0.05 x 50 = 100 V. RMS = 100/sqrt(2) = 70.7 V.

Question 5

Two coils have M = 0.05 H. If the primary current changes from 4 A to 1 A in 0.01 s, find the secondary emf.

Accepted Answer

emf2 = -M dI1/dt = -0.05 x (1 - 4)/0.01 = 15 V.

Practice — Electromagnetic Induction