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 30 cm long lies at 90° to a uniform magnetic field of 0.4 T. The magnetic force on it is 0.12 N. Find the current I.

B = 0.4 TF = 0.12 NL = 30 cmθ = 90°

I = A

2.Easy

A solenoid 20 cm long has 400 turns. Which current I gives a magnetic flux density of 3.77 mT inside it?

N = 400L = 20 cmB = 3.77 mTμ₀ = 4π × 10⁻⁷ T·m/A

I = A

3.Medium

A coil of 100 turns has an area of 200 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.3 T, which is perpendicular to its plane, in 500 ms. Find the average induced emf ε.

N = 100A = 200 cm²B = 0.3 TΔt = 500 ms

ε = V

4.Medium

A proton moving at 2 × 10⁶ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 5.222 cm. Find the magnetic flux density B.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 2 × 10⁶ m/sr = 5.222 cm

B = T

5.Hard

A coil of 100 turns, 8 cm × 5 cm, rotates at 1500 rpm in a uniform field of 0.4 T about an axis perpendicular to the field. Find the peak emf E₀.

N = 100A = 8 cm × 5 cmB = 0.4 Tn = 1500 rpm

E₀ = V

6.Hard

A coil of 250 turns, 12 cm × 25 cm, rotates at 600 rpm in a uniform field of 0.4 T about an axis perpendicular to the field. Find the peak emf E₀.

N = 250A = 12 cm × 25 cmB = 0.4 Tn = 600 rpm

E₀ = V

Answer key

1. I = 1 A
2. I = 1.5 A
3. ε = 2.4 V
4. B = 0.4 T
5. E₀ = 25.13 V
6. E₀ = 188.5 V

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