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
I = 40 APr = 2.5 cmB = ?

A long straight wire carries a current of 40 A. Find the magnetic flux density B at point P, 2.5 cm from the wire.

I = 40 Ar = 2.5 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
B0.8 T8 A90°L = 80 cm

A straight wire 80 cm long carries 8 A at an angle of 90° to a uniform magnetic field of 0.8 T. Find the magnitude of the force F on the wire.

B = 0.8 TI = 8 AL = 80 cmθ = 90°
F = N
3.Medium
−v = 1 × 10⁶ m/sB = 1 mT

An electron moves on a circle in a uniform magnetic field of 1 mT. Find the time T it takes for one revolution.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ CB = 1 mT
T = ns
4.Medium
−v = 2.5 × 10⁶ m/sB = 2 mT

An electron moves on a circle in a uniform magnetic field of 2 mT. Find the time T it takes for one revolution.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ CB = 2 mT
T = ns
5.Hard
L = 40 mH1 → 1.5 A

The current in a 40 mH inductor changes steadily from 1 A to 1.5 A in 20 ms. Find the magnitude of the self-induced emf ε.

L = 40 mH1 A → 1.5 AΔt = 20 ms
ε = V
6.Hard
N1​ = 500, l = 50 cmN2​ = 50M = ?

A short coil of 50 turns is wound tightly round the middle of a long solenoid of 500 turns, length 50 cm and diameter 2 cm. Find their mutual inductance M.

N1 = 500N2 = 50l = 50 cm⌀ = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A
M = µH

Answer key

  1. 1. B = 320 µT
  2. 2. F = 5.12 N
  3. 3. T = 35.73 ns
  4. 4. T = 17.86 ns
  5. 5. ε = 1 V
  6. 6. M = 19.74 µH

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