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 = 2 AR = 2 cmB = ?N = 10

A flat circular coil of 10 turns and radius 2 cm carries a current of 2 A. Find the magnetic flux density B at its centre.

N = 10I = 2 AR = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
I = ?Pr = 20 cmB = 12 µT

The magnetic flux density 20 cm from a long straight wire is 12 µT. Find the current I in the wire.

B = 12 µTr = 20 cmμ₀ = 4π × 10⁻⁷ T·m/A
I = A
3.Medium
20 A15 Ad = 12 cm

Two long parallel wires 12 cm apart carry currents of 20 A and 15 A in the same direction. Find the force per metre of length F/L between them.

I1 = 20 AI2 = 15 Ad = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
4.Medium
+v = 4 × 10⁵ m/sr = ?B = 0.1 T

A proton moves at 4 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.1 T. Find the radius r of its circular path.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 4 × 10⁵ m/sB = 0.1 T
r = cm
5.Hard
l = 30 cmN = 1500, ⌀ 1.5 cm

A long air-core solenoid has 1500 turns, a length of 30 cm and a diameter of 1.5 cm. Find its self-inductance L.

N = 1500l = 30 cm⌀ = 1.5 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = mH
6.Hard
L = 5 mH4.5 → 0.5 A

The current in a 5 mH inductor changes steadily from 4.5 A to 0.5 A in 20 ms. Find the magnitude of the self-induced emf ε.

L = 5 mH4.5 A → 0.5 AΔt = 20 ms
ε = V

Answer key

  1. 1. B = 628.3 µT
  2. 2. I = 12 A
  3. 3. F/L = 500 µN/m
  4. 4. r = 4.177 cm
  5. 5. L = 1.665 mH
  6. 6. ε = 1 V

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