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 solenoid 12 cm long has 400 turns and carries 4 A. Find the magnetic flux density B inside it, far from the ends.

N = 400L = 12 cmI = 4 Aμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

2.Easy

A flat circular coil of 25 turns and radius 8 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 25I = 1.5 AR = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A coil of 200 turns has an area of 150 cm². A uniform field perpendicular to the coil rises steadily from 0.1 T to 0.6 T in 10 ms. Find the average induced emf ε.

N = 200A = 150 cm²B: 0.1 T → 0.6 TΔt = 10 ms

ε = V

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 a 25 mH inductor changes steadily from 0 A to 0.5 A in 1 ms. Find the magnitude of the self-induced emf ε.

L = 25 mH0 A → 0.5 AΔt = 1 ms

ε = V

6.Hard

A coil of 100 turns, 20 cm × 5 cm, rotates at 3600 rpm in a uniform field of 0.1 T about an axis perpendicular to the field. Find the rms value E_rms of the emf.

N = 100A = 20 cm × 5 cmB = 0.1 Tn = 3600 rpm

E_rms = V

Answer key

1. B = 16.76 mT
2. B = 294.5 µT
3. ε = 150 V
4. clockwise
5. ε = 12.5 V
6. E_rms = 26.66 V

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