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

An alpha particle moves at 8 × 10⁶ m/s at an angle of 60° to a uniform magnetic field of 0.02 T. Find the magnitude of the magnetic force F on it.

|q| = 3.204 × 10⁻¹⁹ Cv = 8 × 10⁶ m/sB = 0.02 Tθ = 60°

F = fN

2.Easy

A long straight wire carries a current of 40 A. Find the magnetic flux density B at point P, 3 cm from the wire.

I = 40 Ar = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

Two long parallel wires 15 cm apart carry currents of 25 A and 5 A in opposite directions. Find the force per metre of length F/L between them.

I₁ = 25 AI₂ = 5 Ad = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A

F/L = µN/m

4.Medium

An electron moves at 5 × 10⁶ m/s perpendicular to a uniform magnetic field of 1 mT. Find the radius r of its circular path.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ Cv = 5 × 10⁶ m/sB = 1 mT

r = cm

5.Hard

Two coils with self-inductances of 20 mH and 100 mH have a coupling coefficient of 0.8. The current in the first coil changes at 50 A/s. Find the emf ε induced in the second coil.

L₁ = 20 mHL₂ = 100 mHk = 0.8di/dt = 50 A/s

ε = V

6.Hard

In a velocity selector, crossed fields E = 1 × 10⁴ V/m and B = 0.1 T let only ions of one speed pass straight through. Find that speed v.

E = 1 × 10⁴ V/mB₁ = 0.1 T

v = m/s

Answer key

1. F = 44.4 fN
2. B = 266.7 µT
3. F/L = 166.7 µN/m
4. r = 2.843 cm
5. ε = 1.789 V
6. v = 100000 m/s

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