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 long straight wire carries 5 A. At what distance r from the wire is the magnetic flux density 10 µT?

I = 5 AB = 10 µTμ₀ = 4π × 10⁻⁷ T·m/A

r = cm

2.Easy

A flat circular coil of 5 turns and radius 12 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 5I = 1.5 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A coil of 100 turns, area 40 cm² and resistance 2 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0.1 T to 0.2 T in 10 ms. Find the average induced current I.

N = 100A = 40 cm²B: 0.1 T → 0.2 TΔt = 10 msR = 2 Ω

I = A

4.Medium

A square loop moves to the right into a region with a uniform magnetic field pointing into 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: into the pageentering the field

1clockwise
2counterclockwise

5.Hard

A coil of 100 turns, 20 cm × 5 cm, rotates at 1800 rpm in a uniform field of 0.5 T about an axis perpendicular to the field. Find the peak emf E₀.

N = 100A = 20 cm × 5 cmB = 0.5 Tn = 1800 rpm

E₀ = V

6.Hard

The current in a 200 mH inductor changes steadily from 0.5 A to 1.5 A in 2 ms. Find the magnitude of the self-induced emf ε.

L = 200 mH0.5 A → 1.5 AΔt = 2 ms

ε = V

Answer key

1. r = 10 cm
2. B = 39.27 µT
3. I = 2 A
4. counterclockwise
5. E₀ = 94.25 V
6. ε = 100 V

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