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 flat circular coil of 100 turns and radius 4 cm carries a current of 2 A. Find the magnetic flux density B at its centre.

N = 100I = 2 AR = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

2.Easy

A solenoid 12 cm long has 500 turns and carries 4 A. Find the magnetic flux density B inside it, far from the ends.

N = 500L = 12 cmI = 4 Aμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

3.Medium

A coil of 10 turns has an area of 10 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.4 T, which is perpendicular to its plane, in 20 ms. Find the average induced emf ε.

N = 10A = 10 cm²B = 0.4 TΔt = 20 ms

ε = mV

4.Medium

A coil of 25 turns has an area of 200 cm². The coil sits in a uniform field of 0.3 T perpendicular to its plane, and the field is switched off in 500 ms. Find the average induced emf ε.

N = 25A = 200 cm²B = 0.3 TΔt = 500 ms

ε = mV

5.Hard

A coil of 20 turns, 10 cm × 15 cm, rotates at 300 rpm in a uniform field of 0.25 T about an axis perpendicular to the field. Find the rms value E_rms of the emf.

N = 20A = 10 cm × 15 cmB = 0.25 Tn = 300 rpm

E_rms = V

6.Hard

A coil of 500 turns, 15 cm × 10 cm, rotates at 600 rpm in a uniform field of 0.3 T about an axis perpendicular to the field. Find the peak emf E₀.

N = 500A = 15 cm × 10 cmB = 0.3 Tn = 600 rpm

E₀ = V

Answer key

1. B = 3.142 mT
2. B = 20.94 mT
3. ε = 400 mV
4. ε = 300 mV
5. E_rms = 1.666 V
6. E₀ = 141.4 V

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