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 12 cm long has 200 turns. Which current I gives a magnetic flux density of 6.283 mT inside it?

N = 200L = 12 cmB = 6.283 mTμ₀ = 4π × 10⁻⁷ T·m/A

I = A

2.Easy

A flat circular coil of 100 turns and radius 2 cm carries a current of 4 A. Find the magnetic flux density B at its centre.

N = 100I = 4 AR = 2 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

3.Medium

An electron moves down the page through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on it.

v: down the pageB: out of the page

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

4.Medium

An alpha particle moves at 1.5 × 10⁵ m/s perpendicular to a uniform magnetic field of 1 T. Find the radius r of its circular path.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 1.5 × 10⁵ m/sB = 1 T

r = cm

5.Hard

A long air-core solenoid has 800 turns, a length of 25 cm and a diameter of 2 cm. Find the energy W stored in its magnetic field when it carries 5 A.

N = 800l = 25 cm⌀ = 2 cmI = 5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

6.Hard

A coil of 20 turns, 8 cm × 15 cm, rotates in a uniform field of 0.05 T about an axis perpendicular to the field. At what speed n (in revolutions per minute) must it turn to give an rms emf of 1.599 V?

N = 20A = 8 cm × 15 cmB = 0.05 TE_rms = 1.599 V

n = rpm

Answer key

1. I = 3 A
2. B = 12.57 mT
3. to the right
4. r = 0.3111 cm
5. W = 12.63 mJ
6. n = 1800 rpm

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