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 flat circular coil of 10 turns and radius 10 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

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

B = µT

2.Easy

A long straight wire carries 15 A. At what distance r from the wire is the magnetic flux density 75 µT?

I = 15 AB = 75 µTμ₀ = 4π × 10⁻⁷ T·m/A

r = cm

3.Medium

A coil of 200 turns has an area of 50 cm². The coil sits in a uniform field of 0.3 T perpendicular to its plane, and the field is switched off in 200 ms. Find the average induced emf ε.

N = 200A = 50 cm²B = 0.3 TΔt = 200 ms

ε = V

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 coil of 20 turns, 5 cm × 5 cm, rotates at 300 rpm in a uniform field of 0.4 T about an axis perpendicular to the field. Find the rms value E_rms of the emf.

N = 20A = 5 cm × 5 cmB = 0.4 Tn = 300 rpm

E_rms = V

6.Hard

A short coil of 200 turns is wound tightly round the middle of a long solenoid of 2000 turns, length 50 cm and diameter 5 cm. The current in the solenoid changes at 200 A/s. Find the emf ε induced in the short coil.

N₁ = 2000N₂ = 200l = 50 cm⌀ = 5 cmdi/dt = 200 A/sμ₀ = 4π × 10⁻⁷ T·m/A

ε = mV

Answer key

1. B = 94.25 µT
2. r = 4 cm
3. ε = 1.5 V
4. clockwise
5. E_rms = 0.4443 V
6. ε = 394.8 mV

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