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
B1.2 T10 A45°L = 100 cm

A straight wire 100 cm long carries 10 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 = 10 AL = 100 cmθ = 45°
F = N
2.Easy
I = 1 AR = 12 cmB = ?N = 50

A flat circular coil of 50 turns and radius 12 cm carries a current of 1 A. Find the magnetic flux density B at its centre.

N = 50I = 1 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
dB/dt > 0I = ?

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
  1. 1clockwise
  2. 2counterclockwise
4.Medium
nBA = 40 cm², N = 10B = 0.3 T

A coil of 10 turns has an area of 40 cm². The coil sits in a uniform field of 0.3 T perpendicular to its plane, and the field is switched off in 100 ms. Find the average induced emf ε.

N = 10A = 40 cm²B = 0.3 TΔt = 100 ms
ε = mV
5.Hard
l = 50 cmN = 500, ⌀ 3 cm

A long air-core solenoid has 500 turns, a length of 50 cm and a diameter of 3 cm. Find its self-inductance L.

N = 500l = 50 cm⌀ = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = µH
6.Hard
L = 40 mH4.5 → 0.5 A

The current in a 40 mH inductor changes steadily from 4.5 A to 0.5 A in 50 ms. Find the magnitude of the self-induced emf ε.

L = 40 mH4.5 A → 0.5 AΔt = 50 ms
ε = V

Answer key

  1. 1. F = 8.485 N
  2. 2. B = 261.8 µT
  3. 3. clockwise
  4. 4. ε = 120 mV
  5. 5. L = 444.1 µH
  6. 6. ε = 3.2 V

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