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 solenoid 20 cm long carries 2.5 A. How many turns N must it have for a flux density of 3.142 mT inside?

I = 2.5 AL = 20 cmB = 3.142 mTμ₀ = 4π × 10⁻⁷ T·m/A

N =

2.Easy

A proton moves at 1 × 10⁶ m/s at an angle of 45° to a uniform magnetic field of 0.5 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 1 × 10⁶ m/sB = 0.5 Tθ = 45°

F = fN

3.Medium

A coil of 10 turns, area 10 cm² and resistance 5 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0 T to 0.4 T in 10 ms. Find the average induced current I.

N = 10A = 10 cm²B: 0 T → 0.4 TΔt = 10 msR = 5 Ω

I = mA

4.Medium

A proton moves to the right through a uniform magnetic field pointing into the page. Click the direction of the magnetic force on it.

v: to the rightB: into the page

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

5.Hard

A long air-core solenoid has 200 turns, a length of 25 cm and a diameter of 1 cm. Find the energy W stored in its magnetic field when it carries 2.5 A.

N = 200l = 25 cm⌀ = 1 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = µJ

6.Hard

The current in a 200 mH inductor changes steadily from 3 A to 1 A in 50 ms. Find the magnitude of the self-induced emf ε.

L = 200 mH3 A → 1 AΔt = 50 ms

ε = V

Answer key

1. N = 200
2. F = 56.64 fN
3. I = 80 mA
4. up the page
5. W = 49.35 µJ
6. ε = 8 V

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