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 = 5 AR = 2 cmB = ?N = 5

A flat circular coil of 5 turns and radius 2 cm carries a current of 5 A. Find the magnetic flux density B at its centre.

N = 5I = 5 AR = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
I = 5 APr = 3 cmB = ?

A long straight wire carries a current of 5 A. Find the magnetic flux density B at point P, 3 cm from the wire.

I = 5 Ar = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
+v = 5 × 10⁶ m/sB = 0.8 T

A proton moves on a circle in a uniform magnetic field of 0.8 T. Find the time T it takes for one revolution.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CB = 0.8 T
T = ns
4.Medium
+v = 6 × 10⁵ m/sr = 6.266 cmB = ?

A proton moving at 6 × 10⁵ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 6.266 cm. Find the magnetic flux density B.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 6 × 10⁵ m/sr = 6.266 cm
B = T
5.Hard
Bn = 3600 rpm8 cm × 15 cmN = 20B = 0.4 T

A coil of 20 turns, 8 cm × 15 cm, rotates at 3600 rpm in a uniform field of 0.4 T about an axis perpendicular to the field. Find the peak emf E0.

N = 20A = 8 cm × 15 cmB = 0.4 Tn = 3600 rpm
E0 = V
6.Hard
Bn = 1800 rpm8 cm × 25 cmN = 150B = 0.3 T

A coil of 150 turns, 8 cm × 25 cm, rotates at 1800 rpm in a uniform field of 0.3 T about an axis perpendicular to the field. Find the rms value Erms of the emf.

N = 150A = 8 cm × 25 cmB = 0.3 Tn = 1800 rpm
Erms = V

Answer key

  1. 1. B = 785.4 µT
  2. 2. B = 33.33 µT
  3. 3. T = 82.02 ns
  4. 4. B = 0.1 T
  5. 5. E0 = 36.19 V
  6. 6. Erms = 120 V

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