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 = ?Pr = 10 cmB = 8 µT

The magnetic flux density 10 cm from a long straight wire is 8 µT. Find the current I in the wire.

B = 8 µTr = 10 cmμ₀ = 4π × 10⁻⁷ T·m/A
I = A
2.Easy
+v = 6 × 10⁶ m/sB = 1.5 T

An alpha particle moves at 6 × 10⁶ m/s at an angle of 60° to a uniform magnetic field of 1.5 T. Find the magnitude of the magnetic force F on it.

|q| = 3.204 × 10⁻¹⁹ Cv = 6 × 10⁶ m/sB = 1.5 Tθ = 60°
F = pN
3.Medium
nBA = 50 cm², N = 25B = 0.4 T

A coil of 25 turns has an area of 50 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.4 T, which is perpendicular to its plane, in 50 ms. Find the average induced emf ε.

N = 25A = 50 cm²B = 0.4 TΔt = 50 ms
ε = V
4.Medium
nBA = 20 cm², N = 250B: 0.2 → 1 T

A coil of 250 turns has an area of 20 cm². A uniform field perpendicular to the coil rises steadily from 0.2 T to 1 T in 200 ms. Find the average induced emf ε.

N = 250A = 20 cm²B: 0.2 T → 1 TΔt = 200 ms
ε = V
5.Hard
I = 5 Al = 30 cmN = 800, ⌀ 2.5 cm

A long air-core solenoid has 800 turns, a length of 30 cm and a diameter of 2.5 cm. Find the energy W stored in its magnetic field when it carries 5 A.

N = 800l = 30 cm⌀ = 2.5 cmI = 5 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = mJ
6.Hard
I = 5 Al = 40 cmN = 800, ⌀ 4 cm

A long air-core solenoid has 800 turns, a length of 40 cm and a diameter of 4 cm. Find the energy W stored in its magnetic field when it carries 5 A.

N = 800l = 40 cm⌀ = 4 cmI = 5 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = mJ

Answer key

  1. 1. I = 4 A
  2. 2. F = 2.497 pN
  3. 3. ε = 2 V
  4. 4. ε = 2 V
  5. 5. W = 16.45 mJ
  6. 6. W = 31.58 mJ

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