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
−v = 1.5 × 10⁵ m/sB = 0.05 T

An electron moves at 1.5 × 10⁵ m/s at an angle of 60° to a uniform magnetic field of 0.05 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 1.5 × 10⁵ m/sB = 0.05 Tθ = 60°
F = fN
2.Easy
I = 4 APr = 1 cmB = ?

A long straight wire carries a current of 4 A. Find the magnetic flux density B at point P, 1 cm from the wire.

I = 4 Ar = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
R = 4 Ωv = 10 m/sL = 80 cmB = 0.25 T

A metal rod 80 cm long slides at 10 m/s along two rails in a uniform field of 0.25 T into the page. The rails are joined by a resistor of 4 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.25 TL = 80 cmv = 10 m/sR = 4 Ω
P = W
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
L1​ = 20 mH1000 A/sL2​ = 20 mHk = 0.2ε = ?

Two coils with self-inductances of 20 mH and 20 mH have a coupling coefficient of 0.2. The current in the first coil changes at 1000 A/s. Find the emf ε induced in the second coil.

L1 = 20 mHL2 = 20 mHk = 0.2di/dt = 1000 A/s
ε = V
6.Hard
Bn = 3600 rpm12 cm × 10 cmN = 200B = 0.5 T

A coil of 200 turns, 12 cm × 10 cm, rotates at 3600 rpm in a uniform field of 0.5 T about an axis perpendicular to the field. Find the peak emf E0.

N = 200A = 12 cm × 10 cmB = 0.5 Tn = 3600 rpm
E0 = V

Answer key

  1. 1. F = 1.041 fN
  2. 2. B = 80 µT
  3. 3. P = 1 W
  4. 4. clockwise
  5. 5. ε = 4 V
  6. 6. E0 = 452.4 V

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