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 40 cm long carries 6 A at an angle of 90° to a uniform magnetic field of 0.05 T. Find the magnitude of the force F on the wire.

B = 0.05 TI = 6 AL = 40 cmθ = 90°

F = N

2.Easy

A flat circular coil of 25 turns and radius 12 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 25I = 1.5 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A metal rod 25 cm long slides at 2 m/s along two rails in a uniform field of 0.4 T into the page. The rails are joined by a resistor of 8 Ω; the rod and rails have negligible resistance. Find the current I.

B = 0.4 TL = 25 cmv = 2 m/sR = 8 Ω

I = mA

4.Medium

A metal rod 25 cm long slides at 6 m/s along two rails in a uniform field of 0.1 T into the page. The rails are joined by a resistor of 10 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.1 TL = 25 cmv = 6 m/sR = 10 Ω

P = mW

5.Hard

A long air-core solenoid has 1000 turns, a length of 30 cm and a diameter of 5 cm. Find the energy W stored in its magnetic field when it carries 3 A.

N = 1000l = 30 cm⌀ = 5 cmI = 3 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

6.Hard

A long air-core solenoid has 500 turns, a length of 20 cm and a diameter of 5 cm. Find its self-inductance L.

N = 500l = 20 cm⌀ = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = mH

Answer key

1. F = 0.12 N
2. B = 196.3 µT
3. I = 25 mA
4. P = 2.25 mW
5. W = 37.01 mJ
6. L = 3.084 mH

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