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 straight wire 25 cm long carries 2 A at an angle of 90° to a uniform magnetic field of 0.3 T. Find the magnitude of the force F on the wire.

B = 0.3 TI = 2 AL = 25 cmθ = 90°

F = N

2.Easy

A single circular loop of wire with radius 15 cm carries a current of 2 A. Find the magnetic flux density B at its centre.

N = 1I = 2 AR = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

Two long parallel wires 4 cm apart carry currents of 5 A and 15 A in opposite directions. Find the force per metre of length F/L between them.

I₁ = 5 AI₂ = 15 Ad = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A

F/L = µN/m

4.Medium

A square loop moves to the right into a region with a uniform magnetic field pointing out of the page. Click the direction of the induced current in the loop as seen in the drawing, while the loop is entering the field.

B: out of the pageentering the field

1clockwise
2counterclockwise

5.Hard

A short coil of 50 turns is wound tightly round the middle of a long solenoid of 2000 turns, length 30 cm and diameter 2 cm. Find their mutual inductance M.

N₁ = 2000N₂ = 50l = 30 cm⌀ = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A

M = µH

6.Hard

A long air-core solenoid has 1500 turns, a length of 50 cm and a diameter of 4 cm. Find the energy W stored in its magnetic field when it carries 3 A.

N = 1500l = 50 cm⌀ = 4 cmI = 3 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

Answer key

1. F = 0.15 N
2. B = 8.378 µT
3. F/L = 375 µN/m
4. clockwise
5. M = 131.6 µH
6. W = 31.98 mJ

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