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

An electron moves at 1 × 10⁶ m/s perpendicular to a uniform magnetic field of 1.5 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 1 × 10⁶ m/sB = 1.5 Tθ = 90°

F = fN

2.Easy

A single circular loop of wire with radius 12 cm carries a current of 4 A. Find the magnetic flux density B at its centre.

N = 1I = 4 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A square loop moves to the right into a region with a uniform magnetic field pointing into 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: into the pageentering the field

1clockwise
2counterclockwise

4.Medium

A proton moving at 8 × 10⁵ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 2.089 cm. Find the magnetic flux density B.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 8 × 10⁵ m/sr = 2.089 cm

B = T

5.Hard

A long air-core solenoid has 800 turns, a length of 30 cm and a diameter of 5 cm. Find the energy W stored in its magnetic field when it carries 5 A.

N = 800l = 30 cm⌀ = 5 cmI = 5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

6.Hard

The current in a 40 mH inductor changes steadily from 6 A to 1 A in 2 ms. Find the magnitude of the self-induced emf ε.

L = 40 mH6 A → 1 AΔt = 2 ms

ε = V

Answer key

1. F = 240.3 fN
2. B = 20.94 µT
3. counterclockwise
4. B = 0.3999 T
5. W = 65.8 mJ
6. ε = 100 V

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