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 straight wire 25 cm long lies at 60° to a uniform magnetic field of 0.3 T. The magnetic force on it is 0.7794 N. Find the current I.

B = 0.3 TF = 0.7794 NL = 25 cmθ = 60°

I = A

2.Easy

An electron moves at 4 × 10⁶ m/s at an angle of 60° to a uniform magnetic field of 0.05 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 4 × 10⁶ m/sB = 0.05 Tθ = 60°

F = fN

3.Medium

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

I: to the leftB: out of the page

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

4.Medium

Two long parallel wires 8 cm apart carry currents of 5 A and 15 A in the same direction. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I₁ = 5 AI₂ = 15 Ad = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

5.Hard

A long air-core solenoid has 800 turns, a length of 30 cm and a diameter of 4 cm. Find the energy W stored in its magnetic field when it carries 4 A.

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

W = mJ

6.Hard

The current in an 80 mH inductor changes steadily from 2 A to 5 A in 1 ms. Find the magnitude of the self-induced emf ε.

L = 80 mH2 A → 5 AΔt = 1 ms

ε = V

Answer key

1. I = 12 A
2. F = 27.75 fN
3. up the page
4. B = 50 µT
5. W = 26.95 mJ
6. ε = 240 V

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