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 40 cm long has 500 turns and carries 2.5 A. Find the magnetic flux density B inside it, far from the ends.

N = 500L = 40 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

2.Easy

A solenoid 20 cm long has 800 turns and carries 1.5 A. Find the magnetic flux density B inside it, far from the ends.

N = 800L = 20 cmI = 1.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

3.Medium

A circular loop lies in a uniform magnetic field pointing into the page. The field strength is increasing. Click the direction of the induced current in the loop as seen in the drawing.

B: into the pagedB/dt > 0

1clockwise
2counterclockwise

4.Medium

Two long parallel wires 4 cm apart carry currents of 5 A and 2 A in the same direction. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I₁ = 5 AI₂ = 2 Ad = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

5.Hard

A proton starts from rest, is accelerated through a potential difference of 1000 V and then enters a uniform magnetic field of 0.25 T at right angles. Find the radius r of its path in the field.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 1000 VB = 0.25 T

r = cm

6.Hard

A long air-core solenoid has 800 turns, a length of 15 cm and a diameter of 1.5 cm. Find the energy W stored in its magnetic field when it carries 2.5 A.

N = 800l = 15 cm⌀ = 1.5 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

Answer key

1. B = 3.927 mT
2. B = 7.54 mT
3. counterclockwise
4. B = 30 µT
5. r = 1.828 cm
6. W = 2.961 mJ

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