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

A single circular loop of wire with radius 3 cm carries a current of 1 A. Find the magnetic flux density B at its centre.

N = 1I = 1 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

2.Easy

An electron moves at 2 × 10⁵ m/s at an angle of 60° to a uniform magnetic field of 0.8 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 2 × 10⁵ m/sB = 0.8 Tθ = 60°

F = fN

3.Medium

A coil of 200 turns has an area of 20 cm². A uniform field perpendicular to the coil rises steadily from 0.1 T to 0.5 T in 40 ms. Find the average induced emf ε.

N = 200A = 20 cm²B: 0.1 T → 0.5 TΔt = 40 ms

ε = V

4.Medium

A coil of 25 turns has an area of 40 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.3 T, which is perpendicular to its plane, in 20 ms. Find the average induced emf ε.

N = 25A = 40 cm²B = 0.3 TΔt = 20 ms

ε = V

5.Hard

A long air-core solenoid has 800 turns, a length of 15 cm and a diameter of 5 cm. Find its self-inductance L.

N = 800l = 15 cm⌀ = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = mH

6.Hard

Two coils with self-inductances of 80 mH and 5 mH have a coupling coefficient of 0.6. The current in the first coil changes at 200 A/s. Find the emf ε induced in the second coil.

L₁ = 80 mHL₂ = 5 mHk = 0.6di/dt = 200 A/s

ε = V

Answer key

1. B = 20.94 µT
2. F = 22.2 fN
3. ε = 4 V
4. ε = 3 V
5. L = 10.53 mH
6. ε = 2.4 V

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