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 = 8 × 10⁵ m/sB = 0.1 T

An electron moves at 8 × 10⁵ m/s at an angle of 45° to a uniform magnetic field of 0.1 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 8 × 10⁵ m/sB = 0.1 Tθ = 45°
F = fN
2.Easy
B0.05 TI = ?90°L = 40 cm

A straight wire 40 cm long lies at 90° to a uniform magnetic field of 0.05 T. The magnetic force on it is 0.3 N. Find the current I.

B = 0.05 TF = 0.3 NL = 40 cmθ = 90°
I = A
3.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
4.Medium
vI = ?

A square loop moves to the right into a region with a uniform magnetic field pointing out of the page. Click the direction of the induced current in the loop as seen in the drawing, while the loop is entering the field.

B: out of the pageentering the field
  1. 1clockwise
  2. 2counterclockwise
5.Hard
Bn = ?10 cm × 5 cmN = 150B = 0.5 T

A coil of 150 turns, 10 cm × 5 cm, rotates in a uniform field of 0.5 T about an axis perpendicular to the field. At what speed n (in revolutions per minute) must it turn to give an rms emf of 49.98 V?

N = 150A = 10 cm × 5 cmB = 0.5 TErms = 49.98 V
n = rpm
6.Hard
L = 200 mH0.5 → 1.5 A

The current in a 200 mH inductor changes steadily from 0.5 A to 1.5 A in 50 ms. Find the magnitude of the self-induced emf ε.

L = 200 mH0.5 A → 1.5 AΔt = 50 ms
ε = V

Answer key

  1. 1. F = 9.062 fN
  2. 2. I = 15 A
  3. 3. counterclockwise
  4. 4. clockwise
  5. 5. n = 1800 rpm
  6. 6. ε = 4 V

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