Magnetic fields & induction worksheet with answers

Free printable Magnetic fields & induction worksheet: 6 problems from easy to exam level, with an answer key. Print it or save it as a PDF.

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1.Easy
−v = 3 × 10⁶ m/sB = 0.02 T

An electron moves at 3 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.02 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 3 × 10⁶ m/sB = 0.02 Tθ = 90°
F = fN
2.Easy
B1.2 T10 A90°L = 20 cm

A straight wire 20 cm long carries 10 A at an angle of 90° to a uniform magnetic field of 1.2 T. Find the magnitude of the force F on the wire.

B = 1.2 TI = 10 AL = 20 cmθ = 90°
F = N
3.Medium
dB/dt > 0I = ?

A circular loop lies in a uniform magnetic field pointing into the page. The field strength is increasing. Click the direction of the induced current in the loop as seen in the drawing.

B: into the pagedB/dt > 0
  1. 1clockwise
  2. 2counterclockwise
4.Medium
nBA = 10 cm², N = 20B: 0.1 → 0.9 T

A coil of 20 turns has an area of 10 cm². A uniform field perpendicular to the coil rises steadily from 0.1 T to 0.9 T in 40 ms. Find the average induced emf ε.

N = 20A = 10 cm²B: 0.1 T → 0.9 TΔt = 40 ms
ε = mV
5.Hard
L1​ = 40 mH20 A/sL2​ = 50 mHk = 0.8ε = ?

Two coils with self-inductances of 40 mH and 50 mH have a coupling coefficient of 0.8. The current in the first coil changes at 20 A/s. Find the emf ε induced in the second coil.

L1 = 40 mHL2 = 50 mHk = 0.8di/dt = 20 A/s
ε = V
6.Hard
l = 20 cmN = 500, ⌀ 4 cm

A long air-core solenoid has 500 turns, a length of 20 cm and a diameter of 4 cm. Find its self-inductance L.

N = 500l = 20 cm⌀ = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = mH

Answer key

  1. 1. F = 9.612 fN
  2. 2. F = 2.4 N
  3. 3. counterclockwise
  4. 4. ε = 400 mV
  5. 5. ε = 0.7155 V
  6. 6. L = 1.974 mH

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