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.

New worksheet Practise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________ Date: ____________

1.Easy

A straight wire 30 cm long carries 6 A at an angle of 60° to a uniform magnetic field of 0.4 T. Find the magnitude of the force F on the wire.

B = 0.4 TI = 6 AL = 30 cmθ = 60°

F = N

2.Easy

A flat circular coil of 50 turns and radius 3 cm carries a current of 0.5 A. Find the magnetic flux density B at its centre.

N = 50I = 0.5 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A coil of 500 turns, area 10 cm² and resistance 10 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0.1 T to 0.6 T in 40 ms. Find the average induced current I.

N = 500A = 10 cm²B: 0.1 T → 0.6 TΔt = 40 msR = 10 Ω

I = mA

4.Medium

A metal rod 20 cm long slides at 8 m/s along two rails in a uniform field of 0.2 T into the page. The rails are joined by a resistor of 8 Ω; the rod and rails have negligible resistance. Find the force F needed to keep the rod moving at constant speed (no friction).

B = 0.2 TL = 20 cmv = 8 m/sR = 8 Ω

F = mN

5.Hard

A coil of 150 turns, 20 cm × 10 cm, rotates at 1200 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 = 150A = 20 cm × 10 cmB = 0.4 Tn = 1200 rpm

E_rms = V

6.Hard

A long air-core solenoid has 400 turns, a length of 20 cm and a diameter of 1.5 cm. Find its self-inductance L.

N = 400l = 20 cm⌀ = 1.5 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

Answer key

1. F = 0.6235 N
2. B = 523.6 µT
3. I = 625 mA
4. F = 1.6 mN
5. E_rms = 106.6 V
6. L = 177.7 µH

Full step-by-step solutions: practise this topic on examproblems.com.