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 rectangular loop of 10 cm by 30 cm lies in a uniform magnetic field of 0.3 T. The field makes an angle of 37° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.3 TA = 10 cm × 30 cm37° to the normal

Φ = mWb

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

An electron moves to the right through a uniform magnetic field pointing into the page. Click the direction of the magnetic force on it.

v: to the rightB: into the page

1up the page
2to the right
3down the page
4to the left

4.Medium

Two long parallel wires 8 cm apart carry currents of 8 A and 8 A in the same direction. Find the force per metre of length F/L between them.

I₁ = 8 AI₂ = 8 Ad = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A

F/L = µN/m

5.Hard

The current in a 20 mH inductor changes steadily from 0 A to 5 A in 2 ms. Find the magnitude of the self-induced emf ε.

L = 20 mH0 A → 5 AΔt = 2 ms

ε = V

6.Hard

A coil of 20 turns, 8 cm × 10 cm, rotates in a uniform field of 0.4 T about an axis perpendicular to the field. At what speed n (in revolutions per minute) must it turn to give an rms emf of 5.687 V?

N = 20A = 8 cm × 10 cmB = 0.4 TE_rms = 5.687 V

n = rpm

Answer key

1. Φ = 7.188 mWb
2. F = 3.398 fN
3. down the page
4. F/L = 160 µN/m
5. ε = 50 V
6. n = 1200 rpm

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