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 rectangular loop of 12 cm by 30 cm lies in a uniform magnetic field of 0.25 T. The field makes an angle of 20° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.25 TA = 12 cm × 30 cm20° to the normal

Φ = mWb

2.Easy

A flat circular coil of 100 turns and radius 15 cm carries a current of 0.5 A. Find the magnetic flux density B at its centre.

N = 100I = 0.5 AR = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A metal rod 60 cm long slides at 3 m/s along two rails in a uniform field of 0.5 T into the page. The rails are joined by a resistor of 1 Ω; the rod and rails have negligible resistance. Find the current I.

B = 0.5 TL = 60 cmv = 3 m/sR = 1 Ω

I = mA

4.Medium

A proton moves to the right through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on it.

v: to the rightB: out of the page

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

5.Hard

A long air-core solenoid has 100 turns, a length of 50 cm and a diameter of 4 cm. Find the energy W stored in its magnetic field when it carries 3 A.

N = 100l = 50 cm⌀ = 4 cmI = 3 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = µJ

6.Hard

A coil of 200 turns, 20 cm × 5 cm, rotates at 300 rpm in a uniform field of 0.5 T about an axis perpendicular to the field. Find the peak emf E₀.

N = 200A = 20 cm × 5 cmB = 0.5 Tn = 300 rpm

E₀ = V

Answer key

1. Φ = 8.457 mWb
2. B = 209.4 µT
3. I = 900 mA
4. down the page
5. W = 142.1 µJ
6. E₀ = 31.42 V

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