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 = 20 APr = ?B = 200 µT

A long straight wire carries 20 A. At what distance r from the wire is the magnetic flux density 200 µT?

I = 20 AB = 200 µTμ₀ = 4π × 10⁻⁷ T·m/A
r = cm
2.Easy
I = 15 APr = ?B = 25 µT

A long straight wire carries 15 A. At what distance r from the wire is the magnetic flux density 25 µT?

I = 15 AB = 25 µTμ₀ = 4π × 10⁻⁷ T·m/A
r = cm
3.Medium
25 A2 Ad = 2 cmP

Two long parallel wires 2 cm apart carry currents of 25 A and 2 A in opposite directions. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I1 = 25 AI2 = 2 Ad = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
4.Medium
25 A30 Ad = 12 cmP

Two long parallel wires 12 cm apart carry currents of 25 A and 30 A in opposite directions. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I1 = 25 AI2 = 30 Ad = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
5.Hard
L = 5 mH0 → 0.5 A

The current in a 5 mH inductor changes steadily from 0 A to 0.5 A in 1 ms. Find the magnitude of the self-induced emf ε.

L = 5 mH0 A → 0.5 AΔt = 1 ms
ε = V
6.Hard
L = 5 mH0.5 → 5.5 A

The current in a 5 mH inductor changes steadily from 0.5 A to 5.5 A in 50 ms. Find the magnitude of the self-induced emf ε.

L = 5 mH0.5 A → 5.5 AΔt = 50 ms
ε = V

Answer key

  1. 1. r = 2 cm
  2. 2. r = 12 cm
  3. 3. B = 540 µT
  4. 4. B = 183.3 µT
  5. 5. ε = 2.5 V
  6. 6. ε = 0.5 V

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