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
B0.8 T20 A60°L = 25 cm

A straight wire 25 cm long carries 20 A at an angle of 60° to a uniform magnetic field of 0.8 T. Find the magnitude of the force F on the wire.

B = 0.8 TI = 20 AL = 25 cmθ = 60°
F = N
2.Easy
B0.25 T8 A90°L = 40 cm

A straight wire 40 cm long carries 8 A at an angle of 90° to a uniform magnetic field of 0.25 T. Find the magnitude of the force F on the wire.

B = 0.25 TI = 8 AL = 40 cmθ = 90°
F = N
3.Medium
IBF = ?

A wire carries a current up the page through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on the wire.

I: up the pageB: out of the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
2 A5 Ad = 3 cm

Two long parallel wires 3 cm apart carry currents of 2 A and 5 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 2 AI2 = 5 Ad = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
5.Hard
L = 80 mH0.5 → 5.5 A

The current in an 80 mH inductor changes steadily from 0.5 A to 5.5 A in 10 ms. Find the magnitude of the self-induced emf ε.

L = 80 mH0.5 A → 5.5 AΔt = 10 ms
ε = V
6.Hard
Bn = 300 rpm15 cm × 15 cmN = 200B = 0.25 T

A coil of 200 turns, 15 cm × 15 cm, rotates at 300 rpm in a uniform field of 0.25 T about an axis perpendicular to the field. Find the peak emf E0.

N = 200A = 15 cm × 15 cmB = 0.25 Tn = 300 rpm
E0 = V

Answer key

  1. 1. F = 3.464 N
  2. 2. F = 0.8 N
  3. 3. to the right
  4. 4. F/L = 66.67 µN/m
  5. 5. ε = 40 V
  6. 6. E0 = 35.34 V

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