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 20 cm by 15 cm lies in a uniform magnetic field of 0.05 T. The field makes an angle of 60° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.05 TA = 20 cm × 15 cm60° to the normal

Φ = mWb

2.Easy

A long straight wire carries 40 A. At what distance r from the wire is the magnetic flux density 800 µT?

I = 40 AB = 800 µTμ₀ = 4π × 10⁻⁷ T·m/A

r = cm

3.Medium

A wire carries a current to the left through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on the wire.

I: to the leftB: out of the page

1up the page
2to the right
3down the page
4to the left

4.Medium

Two long parallel wires 8 cm apart carry currents of 10 A and 20 A in opposite directions. Find the force per metre of length F/L between them.

I₁ = 10 AI₂ = 20 Ad = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A

F/L = µN/m

5.Hard

A coil of 50 turns, 8 cm × 10 cm, rotates at 900 rpm in a uniform field of 0.25 T about an axis perpendicular to the field. Find the rms value E_rms of the emf.

N = 50A = 8 cm × 10 cmB = 0.25 Tn = 900 rpm

E_rms = V

6.Hard

The current in a 25 mH inductor changes steadily from 2 A to 1 A in 20 ms. Find the magnitude of the self-induced emf ε.

L = 25 mH2 A → 1 AΔt = 20 ms

ε = V

Answer key

1. Φ = 0.75 mWb
2. r = 1 cm
3. up the page
4. F/L = 500 µN/m
5. E_rms = 6.664 V
6. ε = 1.25 V

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