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 proton moves at 2 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.05 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 2 × 10⁵ m/sB = 0.05 Tθ = 90°

F = fN

2.Easy

A proton moves at 1.5 × 10⁶ m/s at an angle of 45° 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 = 1.5 × 10⁶ m/sB = 0.02 Tθ = 45°

F = fN

3.Medium

A coil of 20 turns has an area of 25 cm². The coil sits in a uniform field of 0.8 T perpendicular to its plane, and the field is switched off in 250 ms. Find the average induced emf ε.

N = 20A = 25 cm²B = 0.8 TΔt = 250 ms

ε = mV

4.Medium

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

B: out of the pagedB/dt > 0

1clockwise
2counterclockwise

5.Hard

A long air-core solenoid has 1000 turns, a length of 30 cm and a diameter of 1.5 cm. Find the energy W stored in its magnetic field when it carries 5 A.

N = 1000l = 30 cm⌀ = 1.5 cmI = 5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

6.Hard

The current in a 200 mH inductor changes steadily from 1 A to 2 A in 50 ms. Find the magnitude of the self-induced emf ε.

L = 200 mH1 A → 2 AΔt = 50 ms

ε = V

Answer key

1. F = 1.602 fN
2. F = 3.398 fN
3. ε = 160 mV
4. clockwise
5. W = 9.253 mJ
6. ε = 4 V

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