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
B0.5 T5 A60°L = 30 cm

A straight wire 30 cm long carries 5 A at an angle of 60° to a uniform magnetic field of 0.5 T. Find the magnitude of the force F on the wire.

B = 0.5 TI = 5 AL = 30 cmθ = 60°
F = N
2.Easy
+v = 8 × 10⁵ m/sB = 0.02 T

A proton moves at 8 × 10⁵ m/s at an angle of 60° to a uniform magnetic field of 0.02 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 8 × 10⁵ m/sB = 0.02 Tθ = 60°
F = fN
3.Medium
R = 2 Ωv = 2 m/sL = 60 cmB = 0.8 T

A metal rod 60 cm long slides at 2 m/s along two rails in a uniform field of 0.8 T into the page. Find the induced emf ε between its ends.

B = 0.8 TL = 60 cmv = 2 m/s
ε = mV
4.Medium
−v = 5 × 10⁶ m/sr = 0.1422 cmB = ?

An electron moving at 5 × 10⁶ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 0.1422 cm. Find the magnetic flux density B.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ Cv = 5 × 10⁶ m/sr = 0.1422 cm
B = mT
5.Hard
L = 40 mH2 → 3 A

The current in a 40 mH inductor changes steadily from 2 A to 3 A in 5 ms. Find the magnitude of the self-induced emf ε.

L = 40 mH2 A → 3 AΔt = 5 ms
ε = V
6.Hard
I = 1 Al = 20 cmN = 200, ⌀ 1 cm

A long air-core solenoid has 200 turns, a length of 20 cm and a diameter of 1 cm. Find the energy W stored in its magnetic field when it carries 1 A.

N = 200l = 20 cm⌀ = 1 cmI = 1 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = µJ

Answer key

  1. 1. F = 0.6495 N
  2. 2. F = 2.22 fN
  3. 3. ε = 960 mV
  4. 4. B = 19.99 mT
  5. 5. ε = 8 V
  6. 6. W = 9.87 µJ

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