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 flat circular coil of 10 turns and radius 8 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 10I = 1.5 AR = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

2.Easy

An electron moves at 4 × 10⁶ m/s at an angle of 60° to a uniform magnetic field of 1.5 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 4 × 10⁶ m/sB = 1.5 Tθ = 60°

F = fN

3.Medium

A coil of 500 turns has an area of 25 cm². A uniform field perpendicular to the coil rises steadily from 0 T to 0.3 T in 40 ms. Find the average induced emf ε.

N = 500A = 25 cm²B: 0 T → 0.3 TΔt = 40 ms

ε = V

4.Medium

An alpha particle moves on a circle in a uniform magnetic field of 0.5 T. Find the time T it takes for one revolution.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ CB = 0.5 T

T = ns

5.Hard

A long air-core solenoid has 400 turns, a length of 15 cm and a diameter of 1 cm. Find the energy W stored in its magnetic field when it carries 2.5 A.

N = 400l = 15 cm⌀ = 1 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = µJ

6.Hard

Two coils with self-inductances of 20 mH and 20 mH have a coupling coefficient of 0.6. The current in the first coil changes at 50 A/s. Find the emf ε induced in the second coil.

L₁ = 20 mHL₂ = 20 mHk = 0.6di/dt = 50 A/s

ε = V

Answer key

1. B = 117.8 µT
2. F = 832.4 fN
3. ε = 9.375 V
4. T = 260.6 ns
5. W = 329 µJ
6. ε = 0.6 V

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