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
I = 5 AR = 2 cmB = ?

A single circular loop of wire with radius 2 cm carries a current of 5 A. Find the magnetic flux density B at its centre.

N = 1I = 5 AR = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
B = 1.005 mTI = ?L = 25 cmN = 400

A solenoid 25 cm long has 400 turns. Which current I gives a magnetic flux density of 1.005 mT inside it?

N = 400L = 25 cmB = 1.005 mTμ₀ = 4π × 10⁻⁷ T·m/A
I = A
3.Medium
R = 10 Ωv = 10 m/sL = 100 cmB = 0.4 T

A metal rod 100 cm long slides at 10 m/s along two rails in a uniform field of 0.4 T into the page. The rails are joined by a resistor of 10 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.4 TL = 100 cmv = 10 m/sR = 10 Ω
P = W
4.Medium
5 A5 Ad = 12 cm

Two long parallel wires 12 cm apart carry currents of 5 A and 5 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 5 AI2 = 5 Ad = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
5.Hard
l = 10 cmN = 2000, ⌀ 3 cm

A long air-core solenoid has 2000 turns, a length of 10 cm and a diameter of 3 cm. Find its self-inductance L.

N = 2000l = 10 cm⌀ = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = mH
6.Hard
l = 20 cmN = 2000, ⌀ 4 cm

A long air-core solenoid has 2000 turns, a length of 20 cm and a diameter of 4 cm. Find its self-inductance L.

N = 2000l = 20 cm⌀ = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = mH

Answer key

  1. 1. B = 157.1 µT
  2. 2. I = 0.4998 A
  3. 3. P = 1.6 W
  4. 4. F/L = 41.67 µN/m
  5. 5. L = 35.53 mH
  6. 6. L = 31.58 mH

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