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 0.05 T. The magnetic force on it is 0.03 N. Find the current I.

B = 0.05 TF = 0.03 NL = 30 cmθ = 90°

I = A

2.Easy

A rectangular loop of 15 cm by 15 cm lies in a uniform magnetic field of 0.4 T. The field makes an angle of 20° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.4 TA = 15 cm × 15 cm20° to the normal

Φ = mWb

3.Medium

A coil of 20 turns, area 10 cm² and resistance 20 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0.05 T to 0.35 T in 40 ms. Find the average induced current I.

N = 20A = 10 cm²B: 0.05 T → 0.35 TΔt = 40 msR = 20 Ω

I = mA

4.Medium

An electron moves at 1 × 10⁶ m/s perpendicular to a uniform magnetic field of 2.5 mT. Find the radius r of its circular path.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ Cv = 1 × 10⁶ m/sB = 2.5 mT

r = cm

5.Hard

A coil of 150 turns, 12 cm × 10 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 = 150A = 12 cm × 10 cmB = 0.05 Tn = 3600 rpm

E₀ = V

6.Hard

A deuteron starts from rest, is accelerated through a potential difference of 2500 V and then enters a uniform magnetic field of 0.3 T at right angles. Find the radius r of its path in the field.

m = 3.344 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 2500 VB = 0.3 T

r = cm

Answer key

1. I = 2 A
2. Φ = 8.457 mWb
3. I = 7.5 mA
4. r = 0.2274 cm
5. E₀ = 33.93 V
6. r = 3.405 cm

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