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 = 3 AR = 3 cmB = ?N = 10

A flat circular coil of 10 turns and radius 3 cm carries a current of 3 A. Find the magnetic flux density B at its centre.

N = 10I = 3 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
B0.25 T10 A30°L = 30 cm

A straight wire 30 cm long carries 10 A at an angle of 30° to a uniform magnetic field of 0.25 T. Find the magnitude of the force F on the wire.

B = 0.25 TI = 10 AL = 30 cmθ = 30°
F = N
3.Medium
+vBF = ?

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

v: down the pageB: into the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
20 A5 Ad = 5 cm

Two long parallel wires 5 cm apart carry currents of 20 A and 5 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 20 AI2 = 5 Ad = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
5.Hard
l = 25 cmN = 100, ⌀ 1 cm

A long air-core solenoid has 100 turns, a length of 25 cm and a diameter of 1 cm. Find its self-inductance L.

N = 100l = 25 cm⌀ = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = µH
6.Hard
I = 1.5 Al = 15 cmN = 1000, ⌀ 3 cm

A long air-core solenoid has 1000 turns, a length of 15 cm and a diameter of 3 cm. Find the energy W stored in its magnetic field when it carries 1.5 A.

N = 1000l = 15 cm⌀ = 3 cmI = 1.5 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = mJ

Answer key

  1. 1. B = 628.3 µT
  2. 2. F = 0.375 N
  3. 3. to the right
  4. 4. F/L = 400 µN/m
  5. 5. L = 3.948 µH
  6. 6. W = 6.662 mJ

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