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 long straight wire carries 4 A. At what distance r from the wire is the magnetic flux density 40 µT?

I = 4 AB = 40 µTμ₀ = 4π × 10⁻⁷ T·m/A

r = cm

2.Easy

An electron moves at 4 × 10⁶ m/s at an angle of 60° to a uniform magnetic field of 0.8 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 4 × 10⁶ m/sB = 0.8 Tθ = 60°

F = fN

3.Medium

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

v: down the pageB: into the page

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

4.Medium

A coil of 200 turns has an area of 50 cm². The coil sits in a uniform field of 0.1 T perpendicular to its plane, and the field is switched off in 50 ms. Find the average induced emf ε.

N = 200A = 50 cm²B = 0.1 TΔt = 50 ms

ε = V

5.Hard

In a velocity selector, crossed fields E = 5 × 10⁴ V/m and B = 0.2 T let only ions of one speed pass straight through. Find that speed v.

E = 5 × 10⁴ V/mB₁ = 0.2 T

v = m/s

6.Hard

Two coils with self-inductances of 200 mH and 50 mH have a coupling coefficient of 0.3. The current in the first coil changes at 50 A/s. Find the emf ε induced in the second coil.

L₁ = 200 mHL₂ = 50 mHk = 0.3di/dt = 50 A/s

ε = V

Answer key

1. r = 2 cm
2. F = 444 fN
3. to the right
4. ε = 2 V
5. v = 250000 m/s
6. ε = 1.5 V

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