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
B0.1 T8 A60°L = 50 cm

A straight wire 50 cm long carries 8 A at an angle of 60° to a uniform magnetic field of 0.1 T. Find the magnitude of the force F on the wire.

B = 0.1 TI = 8 AL = 50 cmθ = 60°
F = N
2.Easy
I = 1.5 AR = 12 cmB = ?N = 100

A flat circular coil of 100 turns and radius 12 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 100I = 1.5 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
15 A30 Ad = 3 cm

Two long parallel wires 3 cm apart carry currents of 15 A and 30 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 15 AI2 = 30 Ad = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
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 = 1200 rpm8 cm × 10 cmN = 50B = 0.25 T

A coil of 50 turns, 8 cm × 10 cm, rotates at 1200 rpm in a uniform field of 0.25 T about an axis perpendicular to the field. Find the rms value Erms of the emf.

N = 50A = 8 cm × 10 cmB = 0.25 Tn = 1200 rpm
Erms = V
6.Hard
E = 5 × 10⁵ V/m, B1​ = 0.5 TB2​ = 0.25 Tr = ?

A proton passes undeflected through a velocity selector with crossed fields E = 5 × 10⁵ V/m and B₁ = 0.5 T. It then enters a second region with only a magnetic field B₂ = 0.25 T, at right angles. Find the radius r of its path there.

E = 5 × 10⁵ V/mB1 = 0.5 TB2 = 0.25 Tm = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ C
r = cm

Answer key

  1. 1. F = 0.3464 N
  2. 2. B = 785.4 µT
  3. 3. F/L = 3000 µN/m
  4. 4. clockwise
  5. 5. Erms = 8.886 V
  6. 6. r = 4.177 cm

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