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 50 cm long lies at 60° to a uniform magnetic field of 0.12 T. The magnetic force on it is 0.7794 N. Find the current I.

B = 0.12 TF = 0.7794 NL = 50 cmθ = 60°

I = A

2.Easy

A long straight wire carries a current of 4 A. Find the magnetic flux density B at point P, 2.5 cm from the wire.

I = 4 Ar = 2.5 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

Two long parallel wires 15 cm apart carry currents of 2 A and 10 A in opposite directions. Find the force per metre of length F/L between them.

I₁ = 2 AI₂ = 10 Ad = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A

F/L = µN/m

4.Medium

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

1clockwise
2counterclockwise

5.Hard

A long air-core solenoid has 800 turns, a length of 40 cm and a diameter of 5 cm. Find the energy W stored in its magnetic field when it carries 5 A.

N = 800l = 40 cm⌀ = 5 cmI = 5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

6.Hard

In a velocity selector, crossed fields E = 1 × 10⁵ V/m and B = 0.05 T let only ions of one speed pass straight through. Find that speed v.

E = 1 × 10⁵ V/mB₁ = 0.05 T

v = m/s

Answer key

1. I = 15 A
2. B = 32 µT
3. F/L = 26.67 µN/m
4. clockwise
5. W = 49.35 mJ
6. v = 2 × 10⁶ m/s

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