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
B0.4 TI = ?60°L = 15 cm

A straight wire 15 cm long lies at 60° to a uniform magnetic field of 0.4 T. The magnetic force on it is 0.6235 N. Find the current I.

B = 0.4 TF = 0.6235 NL = 15 cmθ = 60°
I = A
2.Easy
I = 8 APr = 6 cmB = ?

A long straight wire carries a current of 8 A. Find the magnetic flux density B at point P, 6 cm from the wire.

I = 8 Ar = 6 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
R = 4 Ωv = 8 m/sL = 20 cmB = 0.4 T

A metal rod 20 cm long slides at 8 m/s along two rails in a uniform field of 0.4 T into the page. Find the induced emf ε between its ends.

B = 0.4 TL = 20 cmv = 8 m/s
ε = mV
4.Medium
dB/dt > 0I = ?

A circular loop lies in a uniform magnetic field pointing out of the page. The field strength is increasing. 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
E = 8 × 10⁴ V/m, B1​ = 0.2 T

In a velocity selector, crossed fields E = 8 × 10⁴ V/m and B = 0.2 T let only ions of one speed pass straight through. Find that speed v.

E = 8 × 10⁴ V/mB1 = 0.2 T
v = m/s
6.Hard
I = 3 Al = 30 cmN = 200, ⌀ 2 cm

A long air-core solenoid has 200 turns, a length of 30 cm and a diameter of 2 cm. Find the energy W stored in its magnetic field when it carries 3 A.

N = 200l = 30 cm⌀ = 2 cmI = 3 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = µJ

Answer key

  1. 1. I = 12 A
  2. 2. B = 26.67 µT
  3. 3. ε = 640 mV
  4. 4. clockwise
  5. 5. v = 400000 m/s
  6. 6. W = 236.9 µJ

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