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 100 cm long lies at 90° to a uniform magnetic field of 0.2 T. The magnetic force on it is 1 N. Find the current I.

B = 0.2 TF = 1 NL = 100 cmθ = 90°

I = A

2.Easy

A long straight wire carries 25 A. At what distance r from the wire is the magnetic flux density 62.5 µT?

I = 25 AB = 62.5 µTμ₀ = 4π × 10⁻⁷ T·m/A

r = cm

3.Medium

A proton moves at 1 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.25 T. Find the radius r of its circular path.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 1 × 10⁶ m/sB = 0.25 T

r = cm

4.Medium

An alpha particle moves on a circle in a uniform magnetic field of 0.4 T. Find the time T it takes for one revolution.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ CB = 0.4 T

T = ns

5.Hard

A coil of 500 turns, 5 cm × 15 cm, rotates at 3600 rpm in a uniform field of 0.05 T about an axis perpendicular to the field. Find the peak emf E₀.

N = 500A = 5 cm × 15 cmB = 0.05 Tn = 3600 rpm

E₀ = V

6.Hard

A coil of 200 turns, 5 cm × 20 cm, rotates in a uniform field of 0.25 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 44.43 V?

N = 200A = 5 cm × 20 cmB = 0.25 TE_rms = 44.43 V

n = rpm

Answer key

1. I = 5 A
2. r = 8 cm
3. r = 4.177 cm
4. T = 325.8 ns
5. E₀ = 70.69 V
6. n = 1200 rpm

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