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 4 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.01 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 4 × 10⁶ m/sB = 0.01 Tθ = 90°

F = fN

2.Easy

A long straight wire carries 4 A. At what distance r from the wire is the magnetic flux density 8 µT?

I = 4 AB = 8 µTμ₀ = 4π × 10⁻⁷ T·m/A

r = cm

3.Medium

A wire carries a current down the page through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on the wire.

I: down the pageB: out of the page

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

4.Medium

An alpha particle moving at 8 × 10⁵ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 1.659 cm. Find the magnetic flux density B.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 8 × 10⁵ m/sr = 1.659 cm

B = T

5.Hard

A long air-core solenoid has 800 turns, a length of 20 cm and a diameter of 1 cm. Find the energy W stored in its magnetic field when it carries 2.5 A.

N = 800l = 20 cm⌀ = 1 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = µJ

6.Hard

A coil of 20 turns, 20 cm × 15 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 = 20A = 20 cm × 15 cmB = 0.25 Tn = 3000 rpm

E_rms = V

Answer key

1. F = 6.408 fN
2. r = 10 cm
3. to the left
4. B = 1 T
5. W = 987 µJ
6. E_rms = 33.32 V

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