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 flat circular coil of 50 turns and radius 8 cm carries a current of 2 A. Find the magnetic flux density B at its centre.

N = 50I = 2 AR = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

2.Easy

A flat circular coil of 10 turns and radius 5 cm carries a current of 2.5 A. Find the magnetic flux density B at its centre.

N = 10I = 2.5 AR = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

3.Medium

A metal rod 100 cm long slides at 8 m/s along two rails in a uniform field of 0.5 T into the page. The rails are joined by a resistor of 2 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.5 TL = 100 cmv = 8 m/sR = 2 Ω

P = W

4.Medium

A square loop moves to the right into a region with a uniform magnetic field pointing out of the page. Click the direction of the induced current in the loop as seen in the drawing, while the loop is entering the field.

B: out of the pageentering the field

1clockwise
2counterclockwise

5.Hard

A long air-core solenoid has 500 turns, a length of 20 cm and a diameter of 2.5 cm. Find the energy W stored in its magnetic field when it carries 5 A.

N = 500l = 20 cm⌀ = 2.5 cmI = 5 Aμ₀ = 4π × 10⁻⁷ T·m/A

W = mJ

6.Hard

A coil of 200 turns, 5 cm × 25 cm, rotates at 300 rpm in a uniform field of 0.5 T about an axis perpendicular to the field. Find the rms value E_rms of the emf.

N = 200A = 5 cm × 25 cmB = 0.5 Tn = 300 rpm

E_rms = V

Answer key

1. B = 785.4 µT
2. B = 314.2 µT
3. P = 8 W
4. clockwise
5. W = 9.638 mJ
6. E_rms = 27.77 V

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