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 = 10 APr = ?B = 40 µT

A long straight wire carries 10 A. At what distance r from the wire is the magnetic flux density 40 µT?

I = 10 AB = 40 µTμ₀ = 4π × 10⁻⁷ T·m/A
r = cm
2.Easy
I = ?Pr = 15 cmB = 40 µT

The magnetic flux density 15 cm from a long straight wire is 40 µT. Find the current I in the wire.

B = 40 µTr = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A
I = A
3.Medium
+vBF = ?

A proton moves up the page through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on it.

v: up the pageB: out of the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
30 A12 Ad = 8 cm

Two long parallel wires 8 cm apart carry currents of 30 A and 12 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 30 AI2 = 12 Ad = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
5.Hard
Bn = 1500 rpm10 cm × 10 cmN = 200B = 0.25 T

A coil of 200 turns, 10 cm × 10 cm, rotates at 1500 rpm in a uniform field of 0.25 T about an axis perpendicular to the field. Find the rms value Erms of the emf.

N = 200A = 10 cm × 10 cmB = 0.25 Tn = 1500 rpm
Erms = V
6.Hard
l = 50 cmN = 400, ⌀ 3 cm

A long air-core solenoid has 400 turns, a length of 50 cm and a diameter of 3 cm. Find its self-inductance L.

N = 400l = 50 cm⌀ = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = µH

Answer key

  1. 1. r = 5 cm
  2. 2. I = 30 A
  3. 3. to the right
  4. 4. F/L = 900 µN/m
  5. 5. Erms = 55.54 V
  6. 6. L = 284.2 µH

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