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
B0.1 T20 A30°L = 25 cm

A straight wire 25 cm long carries 20 A at an angle of 30° to a uniform magnetic field of 0.1 T. Find the magnitude of the force F on the wire.

B = 0.1 TI = 20 AL = 25 cmθ = 30°
F = N
2.Easy
I = 10 APr = 1 cmB = ?

A long straight wire carries a current of 10 A. Find the magnetic flux density B at point P, 1 cm from the wire.

I = 10 Ar = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
IBF = ?

A wire carries a current up the page through a uniform magnetic field pointing into the page. Click the direction of the magnetic force on the wire.

I: up the pageB: into the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
−vBF = ?

An electron 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
5.Hard
I = 1.5 Al = 40 cmN = 1500, ⌀ 4 cm

A long air-core solenoid has 1500 turns, a length of 40 cm and a diameter of 4 cm. Find the energy W stored in its magnetic field when it carries 1.5 A.

N = 1500l = 40 cm⌀ = 4 cmI = 1.5 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = mJ
6.Hard
I = 0.5 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 0.5 A.

N = 1000l = 15 cm⌀ = 3 cmI = 0.5 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = µJ

Answer key

  1. 1. F = 0.25 N
  2. 2. B = 200 µT
  3. 3. to the left
  4. 4. to the left
  5. 5. W = 9.993 mJ
  6. 6. W = 740.2 µJ

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