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 2000 turns and carries 2.5 A. Find the magnetic flux density B inside it, far from the ends.

N = 2000L = 12 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

2.Easy

A long straight wire carries a current of 25 A. Find the magnetic flux density B at point P, 10 cm from the wire.

I = 25 Ar = 10 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A coil of 50 turns has an area of 200 cm². The coil sits in a uniform field of 0.8 T perpendicular to its plane, and the field is switched off in 500 ms. Find the average induced emf ε.

N = 50A = 200 cm²B = 0.8 TΔt = 500 ms

ε = V

4.Medium

A coil of 10 turns, area 10 cm² and resistance 4 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0.2 T to 1 T in 500 ms. Find the average induced current I.

N = 10A = 10 cm²B: 0.2 T → 1 TΔt = 500 msR = 4 Ω

I = mA

5.Hard

A long air-core solenoid has 2000 turns, a length of 20 cm and a diameter of 5 cm. Find its self-inductance L.

N = 2000l = 20 cm⌀ = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = mH

6.Hard

A long air-core solenoid has 1000 turns, a length of 10 cm and a diameter of 5 cm. Find the energy W stored in its magnetic field when it carries 1.5 A.

N = 1000l = 10 cm⌀ = 5 cmI = 1.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

Answer key

1. B = 52.36 mT
2. B = 50 µT
3. ε = 1.6 V
4. I = 4 mA
5. L = 49.35 mH
6. W = 27.76 mJ

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