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 = 4 AR = 6 cmB = ?N = 50

A flat circular coil of 50 turns and radius 6 cm carries a current of 4 A. Find the magnetic flux density B at its centre.

N = 50I = 4 AR = 6 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
2.Easy
B = 1.508 mTI = ?L = 25 cmN = 200

A solenoid 25 cm long has 200 turns. Which current I gives a magnetic flux density of 1.508 mT inside it?

N = 200L = 25 cmB = 1.508 mTμ₀ = 4π × 10⁻⁷ T·m/A
I = A
3.Medium
+v = 2.5 × 10⁵ 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
dB/dt < 0I = ?

A circular loop lies in a uniform magnetic field pointing into the page. The field strength is decreasing. Click the direction of the induced current in the loop as seen in the drawing.

B: into the pagedB/dt < 0
  1. 1clockwise
  2. 2counterclockwise
5.Hard
l = 50 cmN = 300, ⌀ 5 cm

A long air-core solenoid has 300 turns, a length of 50 cm and a diameter of 5 cm. Find its self-inductance L.

N = 300l = 50 cm⌀ = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = µH
6.Hard
Bn = 1800 rpm20 cm × 10 cmN = 20B = 0.1 T

A coil of 20 turns, 20 cm × 10 cm, rotates at 1800 rpm in a uniform field of 0.1 T about an axis perpendicular to the field. Find the rms value Erms of the emf.

N = 20A = 20 cm × 10 cmB = 0.1 Tn = 1800 rpm
Erms = V

Answer key

  1. 1. B = 2.094 mT
  2. 2. I = 1.5 A
  3. 3. T = 82.02 ns
  4. 4. clockwise
  5. 5. L = 444.1 µH
  6. 6. Erms = 5.331 V

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