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 = 3 × 10⁵ m/sB = 1 T

An electron moves at 3 × 10⁵ m/s perpendicular to a uniform magnetic field of 1 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 3 × 10⁵ m/sB = 1 Tθ = 90°
F = fN
2.Easy
I = 40 APr = ?B = 40 µT

A long straight wire carries 40 A. At what distance r from the wire is the magnetic flux density 40 µT?

I = 40 AB = 40 µTμ₀ = 4π × 10⁻⁷ T·m/A
r = cm
3.Medium
vI = ?

A square loop moves to the right into a region with a uniform magnetic field pointing out of the page. Click the direction of the induced current in the loop as seen in the drawing, while the loop is entering the field.

B: out of the pageentering the field
  1. 1clockwise
  2. 2counterclockwise
4.Medium
nBA = 25 cm², N = 500B: 0 → 0.1 T

A coil of 500 turns, area 25 cm² and resistance 8 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0 T to 0.1 T in 250 ms. Find the average induced current I.

N = 500A = 25 cm²B: 0 T → 0.1 TΔt = 250 msR = 8 Ω
I = mA
5.Hard
N1​ = 1000, l = 20 cm50 A/sN2​ = 200Mε = ?

A short coil of 200 turns is wound tightly round the middle of a long solenoid of 1000 turns, length 20 cm and diameter 4 cm. The current in the solenoid changes at 50 A/s. Find the emf ε induced in the short coil.

N1 = 1000N2 = 200l = 20 cm⌀ = 4 cmdi/dt = 50 A/sμ₀ = 4π × 10⁻⁷ T·m/A
ε = mV
6.Hard
I = 1 Al = 50 cmN = 300, ⌀ 2 cm

A long air-core solenoid has 300 turns, a length of 50 cm and a diameter of 2 cm. Find the energy W stored in its magnetic field when it carries 1 A.

N = 300l = 50 cm⌀ = 2 cmI = 1 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = µJ

Answer key

  1. 1. F = 48.06 fN
  2. 2. r = 20 cm
  3. 3. clockwise
  4. 4. I = 62.5 mA
  5. 5. ε = 78.96 mV
  6. 6. W = 35.53 µJ

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