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
+v = 1 × 10⁵ m/sB = 0.2 T

An alpha particle moves at 1 × 10⁵ m/s at an angle of 30° to a uniform magnetic field of 0.2 T. Find the magnitude of the magnetic force F on it.

|q| = 3.204 × 10⁻¹⁹ Cv = 1 × 10⁵ m/sB = 0.2 Tθ = 30°
F = fN
2.Easy
B0.2 TI = ?45°L = 20 cm

A straight wire 20 cm long lies at 45° to a uniform magnetic field of 0.2 T. The magnetic force on it is 0.1697 N. Find the current I.

B = 0.2 TF = 0.1697 NL = 20 cmθ = 45°
I = A
3.Medium
8 A12 Ad = 3 cm

Two long parallel wires 3 cm apart carry currents of 8 A and 12 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 8 AI2 = 12 Ad = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
4.Medium
nBA = 10 cm², N = 200B: 0.1 → 0.6 T

A coil of 200 turns has an area of 10 cm². A uniform field perpendicular to the coil rises steadily from 0.1 T to 0.6 T in 500 ms. Find the average induced emf ε.

N = 200A = 10 cm²B: 0.1 T → 0.6 TΔt = 500 ms
ε = mV
5.Hard
E = 1 × 10⁴ V/m, B1​ = 0.5 T

In a velocity selector, crossed fields E = 1 × 10⁴ V/m and B = 0.5 T let only ions of one speed pass straight through. Find that speed v.

E = 1 × 10⁴ V/mB1 = 0.5 T
v = m/s
6.Hard
L = 25 mH0.5 → 2.5 A

The current in a 25 mH inductor changes steadily from 0.5 A to 2.5 A in 1 ms. Find the magnitude of the self-induced emf ε.

L = 25 mH0.5 A → 2.5 AΔt = 1 ms
ε = V

Answer key

  1. 1. F = 3.204 fN
  2. 2. I = 6 A
  3. 3. F/L = 640 µN/m
  4. 4. ε = 200 mV
  5. 5. v = 20000 m/s
  6. 6. ε = 50 V

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