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 solenoid 15 cm long carries 1 A. How many turns N must it have for a flux density of 3.351 mT inside?

I = 1 AL = 15 cmB = 3.351 mTμ₀ = 4π × 10⁻⁷ T·m/A

N =

2.Easy

A flat circular coil of 25 turns and radius 10 cm carries a current of 2.5 A. Find the magnetic flux density B at its centre.

N = 25I = 2.5 AR = 10 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

An alpha particle moves at 4 × 10⁶ m/s perpendicular to a uniform magnetic field of 1.5 T. Find the radius r of its circular path.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 4 × 10⁶ m/sB = 1.5 T

r = cm

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 300 turns, a length of 15 cm and a diameter of 2.5 cm. Find its self-inductance L.

N = 300l = 15 cm⌀ = 2.5 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

6.Hard

A long air-core solenoid has 2000 turns, a length of 40 cm and a diameter of 2.5 cm. Find the energy W stored in its magnetic field when it carries 2 A.

N = 2000l = 40 cm⌀ = 2.5 cmI = 2 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

Answer key

1. N = 400
2. B = 392.7 µT
3. r = 5.531 cm
4. clockwise
5. L = 370.1 µH
6. W = 12.34 mJ

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