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
B0.12 TI = ?90°L = 15 cm

A straight wire 15 cm long lies at 90° to a uniform magnetic field of 0.12 T. The magnetic force on it is 0.09 N. Find the current I.

B = 0.12 TF = 0.09 NL = 15 cmθ = 90°
I = A
2.Easy
I = 5 AR = 12 cmB = ?N = 5

A flat circular coil of 5 turns and radius 12 cm carries a current of 5 A. Find the magnetic flux density B at its centre.

N = 5I = 5 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
2 A15 Ad = 5 cm

Two long parallel wires 5 cm apart carry currents of 2 A and 15 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 2 AI2 = 15 Ad = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
4.Medium
−v = 3 × 10⁶ m/sr = ?B = 2.5 mT

An electron moves at 3 × 10⁶ m/s perpendicular to a uniform magnetic field of 2.5 mT. Find the radius r of its circular path.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ Cv = 3 × 10⁶ m/sB = 2.5 mT
r = cm
5.Hard
V = 2000 VB = 0.1 Tr = ?

An alpha particle starts from rest, is accelerated through a potential difference of 2000 V and then enters a uniform magnetic field of 0.1 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 = 2000 VB = 0.1 T
r = cm
6.Hard
L = 50 mH3 → 2 A

The current in a 50 mH inductor changes steadily from 3 A to 2 A in 2 ms. Find the magnitude of the self-induced emf ε.

L = 50 mH3 A → 2 AΔt = 2 ms
ε = V

Answer key

  1. 1. I = 5 A
  2. 2. B = 130.9 µT
  3. 3. F/L = 120 µN/m
  4. 4. r = 0.6823 cm
  5. 5. r = 9.108 cm
  6. 6. ε = 25 V

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