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
B = ?I = 1 AL = 12 cmN = 250

A solenoid 12 cm long has 250 turns and carries 1 A. Find the magnetic flux density B inside it, far from the ends.

N = 250L = 12 cmI = 1 Aμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
2.Easy
I = 8 APr = 10 cmB = ?

A long straight wire carries a current of 8 A. Find the magnetic flux density B at point P, 10 cm from the wire.

I = 8 Ar = 10 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
nBA = 50 cm², N = 200B: 0.2 → 0.8 T

A coil of 200 turns has an area of 50 cm². A uniform field perpendicular to the coil rises steadily from 0.2 T to 0.8 T in 200 ms. Find the average induced emf ε.

N = 200A = 50 cm²B: 0.2 T → 0.8 TΔt = 200 ms
ε = V
4.Medium
nBA = 200 cm², N = 25B = 0.4 T

A coil of 25 turns has an area of 200 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.4 T, which is perpendicular to its plane, in 250 ms. Find the average induced emf ε.

N = 25A = 200 cm²B = 0.4 TΔt = 250 ms
ε = V
5.Hard
Bn = 300 rpm8 cm × 10 cmN = 200B = 0.4 T

A coil of 200 turns, 8 cm × 10 cm, rotates at 300 rpm in a uniform field of 0.4 T about an axis perpendicular to the field. Find the peak emf E0.

N = 200A = 8 cm × 10 cmB = 0.4 Tn = 300 rpm
E0 = V
6.Hard
L = 200 mH0.5 → 4.5 A

The current in a 200 mH inductor changes steadily from 0.5 A to 4.5 A in 2 ms. Find the magnitude of the self-induced emf ε.

L = 200 mH0.5 A → 4.5 AΔt = 2 ms
ε = V

Answer key

  1. 1. B = 2.618 mT
  2. 2. B = 16 µT
  3. 3. ε = 3 V
  4. 4. ε = 1.6 V
  5. 5. E0 = 20.11 V
  6. 6. ε = 400 V

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