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
B = ?I = 1 AL = 10 cmN = 500

A solenoid 10 cm long has 500 turns and carries 1 A. Find the magnetic flux density B inside it, far from the ends.

N = 500L = 10 cmI = 1 Aμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
2.Easy
B0.5 T5 A90°L = 100 cm

A straight wire 100 cm long carries 5 A at an angle of 90° to a uniform magnetic field of 0.5 T. Find the magnitude of the force F on the wire.

B = 0.5 TI = 5 AL = 100 cmθ = 90°
F = N
3.Medium
nBA = 50 cm², N = 200B = 0.8 T

A coil of 200 turns has an area of 50 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.8 T, which is perpendicular to its plane, in 100 ms. Find the average induced emf ε.

N = 200A = 50 cm²B = 0.8 TΔt = 100 ms
ε = V
4.Medium
−v = 1.5 × 10⁶ m/sB = 2 mT

An electron moves on a circle in a uniform magnetic field of 2 mT. Find the time T it takes for one revolution.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ CB = 2 mT
T = ns
5.Hard
l = 40 cmN = 800, ⌀ 5 cm

A long air-core solenoid has 800 turns, a length of 40 cm and a diameter of 5 cm. Find its self-inductance L.

N = 800l = 40 cm⌀ = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = mH
6.Hard
E = 1 × 10⁴ V/m, B1​ = 0.4 T

In a velocity selector, crossed fields E = 1 × 10⁴ V/m and B = 0.4 T let only ions of one speed pass straight through. Find that speed v.

E = 1 × 10⁴ V/mB1 = 0.4 T
v = m/s

Answer key

  1. 1. B = 6.283 mT
  2. 2. F = 2.5 N
  3. 3. ε = 16 V
  4. 4. T = 17.86 ns
  5. 5. L = 3.948 mH
  6. 6. v = 25000 m/s

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