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 straight wire 80 cm long carries 6 A at an angle of 45° to a uniform magnetic field of 1.2 T. Find the magnitude of the force F on the wire.

B = 1.2 TI = 6 AL = 80 cmθ = 45°

F = N

2.Easy

A single circular loop of wire with radius 3 cm carries a current of 4 A. Find the magnetic flux density B at its centre.

N = 1I = 4 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A metal rod 40 cm long slides at 10 m/s along two rails in a uniform field of 0.2 T into the page. The rails are joined by a resistor of 5 Ω; the rod and rails have negligible resistance. Find the current I.

B = 0.2 TL = 40 cmv = 10 m/sR = 5 Ω

I = mA

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

The current in an 80 mH inductor changes steadily from 1 A to 6 A in 20 ms. Find the magnitude of the self-induced emf ε.

L = 80 mH1 A → 6 AΔt = 20 ms

ε = V

6.Hard

A coil of 50 turns, 20 cm × 20 cm, rotates at 3000 rpm in a uniform field of 0.05 T about an axis perpendicular to the field. Find the peak emf E₀.

N = 50A = 20 cm × 20 cmB = 0.05 Tn = 3000 rpm

E₀ = V

Answer key

1. F = 4.073 N
2. B = 83.78 µT
3. I = 160 mA
4. clockwise
5. ε = 20 V
6. E₀ = 31.42 V

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