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

The magnetic flux density 8 cm from a long straight wire is 30 µT. Find the current I in the wire.

B = 30 µTr = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A

I = A

2.Easy

An electron moves at 4 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.1 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 4 × 10⁵ m/sB = 0.1 Tθ = 90°

F = fN

3.Medium

An alpha particle moves at 3 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.25 T. Find the radius r of its circular path.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 3 × 10⁵ m/sB = 0.25 T

r = cm

4.Medium

An alpha particle moving at 2 × 10⁶ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 8.296 cm. Find the magnetic flux density B.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 2 × 10⁶ m/sr = 8.296 cm

B = T

5.Hard

A proton passes undeflected through a velocity selector with crossed fields E = 1 × 10⁵ V/m and B₁ = 0.05 T. It then enters a second region with only a magnetic field B₂ = 0.25 T, at right angles. Find the radius r of its path there.

E = 1 × 10⁵ V/mB₁ = 0.05 TB₂ = 0.25 Tm = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ C

r = cm

6.Hard

A long air-core solenoid has 100 turns, a length of 50 cm and a diameter of 1 cm. Find its self-inductance L.

N = 100l = 50 cm⌀ = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

Answer key

1. I = 12 A
2. F = 6.408 fN
3. r = 2.489 cm
4. B = 0.5 T
5. r = 8.355 cm
6. L = 1.974 µH

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