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 = 2 × 10⁶ m/sB = 0.2 T

An electron moves at 2 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.2 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 2 × 10⁶ m/sB = 0.2 Tθ = 90°
F = fN
2.Easy
−v = 8 × 10⁶ m/sB = 0.1 T

An electron moves at 8 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.1 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 8 × 10⁶ m/sB = 0.1 Tθ = 90°
F = fN
3.Medium
nBA = 80 cm², N = 200B: 0.2 → 0.7 T

A coil of 200 turns, area 80 cm² and resistance 8 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0.2 T to 0.7 T in 40 ms. Find the average induced current I.

N = 200A = 80 cm²B: 0.2 T → 0.7 TΔt = 40 msR = 8 Ω
I = A
4.Medium
8 A25 Ad = 4 cm

Two long parallel wires 4 cm apart carry currents of 8 A and 25 A in the same direction. Find the force per metre of length F/L between them.

I1 = 8 AI2 = 25 Ad = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
5.Hard
V = 2000 VB = 0.4 Tr = ?

An alpha particle starts from rest, is accelerated through a potential difference of 2000 V and then enters a uniform magnetic field of 0.4 T at right angles. Find the radius r of its path in the field.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ CV = 2000 VB = 0.4 T
r = cm
6.Hard
V = 2000 VB = 0.1 Tr = ?

An alpha particle starts from rest, is accelerated through a potential difference of 2000 V and then enters a uniform magnetic field of 0.1 T at right angles. Find the radius r of its path in the field.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ CV = 2000 VB = 0.1 T
r = cm

Answer key

  1. 1. F = 64.08 fN
  2. 2. F = 128.2 fN
  3. 3. I = 2.5 A
  4. 4. F/L = 1000 µN/m
  5. 5. r = 2.277 cm
  6. 6. r = 9.108 cm

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