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
B0.25 T4 A60°L = 50 cm

A straight wire 50 cm long carries 4 A at an angle of 60° to a uniform magnetic field of 0.25 T. Find the magnitude of the force F on the wire.

B = 0.25 TI = 4 AL = 50 cmθ = 60°
F = N
2.Easy
B = ?I = 1.5 AL = 10 cmN = 400

A solenoid 10 cm long has 400 turns and carries 1.5 A. Find the magnetic flux density B inside it, far from the ends.

N = 400L = 10 cmI = 1.5 Aμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
3.Medium
+v = 1 × 10⁶ m/sr = ?B = 0.4 T

A proton moves at 1 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.4 T. Find the radius r of its circular path.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 1 × 10⁶ m/sB = 0.4 T
r = cm
4.Medium
+v = 3 × 10⁶ m/sr = ?B = 0.2 T

An alpha particle moves at 3 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.2 T. Find the radius r of its circular path.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 3 × 10⁶ m/sB = 0.2 T
r = cm
5.Hard
E = 1 × 10⁴ V/m, B1​ = 0.5 T

In a velocity selector, crossed fields E = 1 × 10⁴ V/m and B = 0.5 T let only ions of one speed pass straight through. Find that speed v.

E = 1 × 10⁴ V/mB1 = 0.5 T
v = m/s
6.Hard
I = 1.5 Al = 20 cmN = 800, ⌀ 2.5 cm

A long air-core solenoid has 800 turns, a length of 20 cm and a diameter of 2.5 cm. Find the energy W stored in its magnetic field when it carries 1.5 A.

N = 800l = 20 cm⌀ = 2.5 cmI = 1.5 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = mJ

Answer key

  1. 1. F = 0.433 N
  2. 2. B = 7.54 mT
  3. 3. r = 2.611 cm
  4. 4. r = 31.11 cm
  5. 5. v = 20000 m/s
  6. 6. W = 2.221 mJ

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