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 long straight wire carries a current of 12 A. Find the magnetic flux density B at point P, 6 cm from the wire.

I = 12 Ar = 6 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

2.Easy

An electron moves at 1 × 10⁶ m/s at an angle of 45° to a uniform magnetic field of 0.1 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 1 × 10⁶ m/sB = 0.1 Tθ = 45°

F = fN

3.Medium

A proton moves on a circle in a uniform magnetic field of 0.1 T. Find the time T it takes for one revolution.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CB = 0.1 T

T = ns

4.Medium

A metal rod 60 cm long slides at 1 m/s along two rails in a uniform field of 0.25 T into the page. The rails are joined by a resistor of 2.5 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.25 TL = 60 cmv = 1 m/sR = 2.5 Ω

P = mW

5.Hard

A long air-core solenoid has 2000 turns, a length of 15 cm and a diameter of 4 cm. Find the energy W stored in its magnetic field when it carries 0.5 A.

N = 2000l = 15 cm⌀ = 4 cmI = 0.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

6.Hard

A long air-core solenoid has 500 turns, a length of 30 cm and a diameter of 1 cm. Find its self-inductance L.

N = 500l = 30 cm⌀ = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

Answer key

1. B = 40 µT
2. F = 11.33 fN
3. T = 656.2 ns
4. P = 9 mW
5. W = 5.264 mJ
6. L = 82.25 µH

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