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 carries 3 A. How many turns N must it have for a flux density of 1.885 mT inside?

I = 3 AL = 40 cmB = 1.885 mTμ₀ = 4π × 10⁻⁷ T·m/A

N =

2.Easy

A rectangular loop of 5 cm by 20 cm lies in a uniform magnetic field of 0.4 T. The field makes an angle of 60° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.4 TA = 5 cm × 20 cm60° to the normal

Φ = mWb

3.Medium

A metal rod 40 cm long slides at 10 m/s along two rails in a uniform field of 0.25 T into the page. Find the induced emf ε between its ends.

B = 0.25 TL = 40 cmv = 10 m/s

ε = V

4.Medium

A metal rod 25 cm long slides at 2.5 m/s along two rails in a uniform field of 0.1 T into the page. The rails are joined by a resistor of 4 Ω; the rod and rails have negligible resistance. Find the current I.

B = 0.1 TL = 25 cmv = 2.5 m/sR = 4 Ω

I = mA

5.Hard

The current in a 10 mH inductor changes steadily from 2 A to 3 A in 20 ms. Find the magnitude of the self-induced emf ε.

L = 10 mH2 A → 3 AΔt = 20 ms

ε = V

6.Hard

A coil of 250 turns, 20 cm × 5 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 = 20 cm × 5 cmB = 0.4 Tn = 600 rpm

E₀ = V

Answer key

1. N = 200
2. Φ = 2 mWb
3. ε = 1 V
4. I = 15.63 mA
5. ε = 0.5 V
6. E₀ = 62.83 V

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