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

A rectangular loop of 15 cm by 25 cm lies in a uniform magnetic field of 0.1 T. The field makes an angle of 0° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.1 TA = 15 cm × 25 cm0° to the normal

Φ = mWb

2.Easy

A straight wire 20 cm long carries 10 A at an angle of 30° to a uniform magnetic field of 0.12 T. Find the magnitude of the force F on the wire.

B = 0.12 TI = 10 AL = 20 cmθ = 30°

F = N

3.Medium

Two long parallel wires 4 cm apart carry currents of 25 A and 10 A in opposite directions. Find the force per metre of length F/L between them.

I₁ = 25 AI₂ = 10 Ad = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A

F/L = µN/m

4.Medium

Two long parallel wires 12 cm apart carry currents of 30 A and 30 A in opposite directions. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I₁ = 30 AI₂ = 30 Ad = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

5.Hard

In a velocity selector, crossed fields E = 1 × 10⁵ V/m and B = 0.2 T let only ions of one speed pass straight through. Find that speed v.

E = 1 × 10⁵ V/mB₁ = 0.2 T

v = m/s

6.Hard

A long air-core solenoid has 500 turns, a length of 40 cm and a diameter of 1 cm. Find its self-inductance L.

N = 500l = 40 cm⌀ = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

Answer key

1. Φ = 3.75 mWb
2. F = 0.12 N
3. F/L = 1250 µN/m
4. B = 200 µT
5. v = 500000 m/s
6. L = 61.69 µH

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