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 a current of 8 A. Find the magnetic flux density B at point P, 5 cm from the wire.

I = 8 Ar = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

2.Easy

A solenoid 15 cm long has 600 turns. Which current I gives a magnetic flux density of 15.08 mT inside it?

N = 600L = 15 cmB = 15.08 mTμ₀ = 4π × 10⁻⁷ T·m/A

I = A

3.Medium

A circular loop lies in a uniform magnetic field pointing into the page. The field strength is decreasing. Click the direction of the induced current in the loop as seen in the drawing.

B: into the pagedB/dt < 0

1clockwise
2counterclockwise

4.Medium

A metal rod 20 cm long slides at 1 m/s along two rails in a uniform field of 0.6 T into the page. The rails are joined by a resistor of 0.5 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.6 TL = 20 cmv = 1 m/sR = 0.5 Ω

P = mW

5.Hard

A coil of 100 turns, 12 cm × 20 cm, rotates at 3000 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 = 100A = 12 cm × 20 cmB = 0.25 Tn = 3000 rpm

E_rms = V

6.Hard

A long air-core solenoid has 300 turns, a length of 20 cm and a diameter of 2.5 cm. Find its self-inductance L.

N = 300l = 20 cm⌀ = 2.5 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

Answer key

1. B = 32 µT
2. I = 3 A
3. clockwise
4. P = 28.8 mW
5. E_rms = 133.3 V
6. L = 277.6 µH

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