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
B0.08 T15 A90°L = 20 cm

A straight wire 20 cm long carries 15 A at an angle of 90° to a uniform magnetic field of 0.08 T. Find the magnitude of the force F on the wire.

B = 0.08 TI = 15 AL = 20 cmθ = 90°
F = N
2.Easy
nB53°10 cm × 25 cmB = 0.5 T

A rectangular loop of 10 cm by 25 cm lies in a uniform magnetic field of 0.5 T. The field lines make an angle of 37° with the plane of the loop. Find the magnetic flux Φ through the loop.

B = 0.5 TA = 10 cm × 25 cm37° to the plane
Φ = mWb
3.Medium
25 A25 Ad = 2 cm

Two long parallel wires 2 cm apart carry currents of 25 A and 25 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 25 AI2 = 25 Ad = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
4.Medium
12 A2 Ad = 10 cmP

Two long parallel wires 10 cm apart carry currents of 12 A and 2 A in opposite directions. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I1 = 12 AI2 = 2 Ad = 10 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
5.Hard
V = 2500 VB = 0.3 Tr = ?

An alpha particle starts from rest, is accelerated through a potential difference of 2500 V and then enters a uniform magnetic field of 0.3 T at right angles. Find the radius r of its path in the field.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ CV = 2500 VB = 0.3 T
r = cm
6.Hard
L1​ = 200 mH50 A/sL2​ = 50 mHk = 0.75ε = ?

Two coils with self-inductances of 200 mH and 50 mH have a coupling coefficient of 0.75. The current in the first coil changes at 50 A/s. Find the emf ε induced in the second coil.

L1 = 200 mHL2 = 50 mHk = 0.75di/dt = 50 A/s
ε = V

Answer key

  1. 1. F = 0.24 N
  2. 2. Φ = 7.523 mWb
  3. 3. F/L = 6250 µN/m
  4. 4. B = 56 µT
  5. 5. r = 3.394 cm
  6. 6. ε = 3.75 V

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