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 = 4 APr = ?B = 4 µT

A long straight wire carries 4 A. At what distance r from the wire is the magnetic flux density 4 µT?

I = 4 AB = 4 µTμ₀ = 4π × 10⁻⁷ T·m/A
r = cm
2.Easy
B0.4 T10 A90°L = 80 cm

A straight wire 80 cm long carries 10 A at an angle of 90° to a uniform magnetic field of 0.4 T. Find the magnitude of the force F on the wire.

B = 0.4 TI = 10 AL = 80 cmθ = 90°
F = N
3.Medium
dB/dt > 0I = ?

A circular loop lies in a uniform magnetic field pointing into the page. The field strength is increasing. Click the direction of the induced current in the loop as seen in the drawing.

B: into the pagedB/dt > 0
  1. 1clockwise
  2. 2counterclockwise
4.Medium
dB/dt < 0I = ?

A circular loop lies in a uniform magnetic field pointing out of the page. The field strength is decreasing. Click the direction of the induced current in the loop as seen in the drawing.

B: out of the pagedB/dt < 0
  1. 1clockwise
  2. 2counterclockwise
5.Hard
V = 1000 VB = 0.2 Tr = ?

A proton starts from rest, is accelerated through a potential difference of 1000 V and then enters a uniform magnetic field of 0.2 T at right angles. Find the radius r of its path in the field.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 1000 VB = 0.2 T
r = cm
6.Hard
I = 1 Al = 50 cmN = 400, ⌀ 2 cm

A long air-core solenoid has 400 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 = 400l = 50 cm⌀ = 2 cmI = 1 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = µJ

Answer key

  1. 1. r = 20 cm
  2. 2. F = 3.2 N
  3. 3. counterclockwise
  4. 4. counterclockwise
  5. 5. r = 2.285 cm
  6. 6. W = 63.17 µJ

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