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 100 turns and radius 10 cm carries a current of 0.5 A. Find the magnetic flux density B at its centre.

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

B = µT

2.Easy

A flat circular coil of 100 turns and radius 12 cm carries a current of 2.5 A. Find the magnetic flux density B at its centre.

N = 100I = 2.5 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

3.Medium

An alpha particle moves at 6 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.2 T. Find the radius r of its circular path.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 6 × 10⁶ m/sB = 0.2 T

r = cm

4.Medium

Two long parallel wires 15 cm apart carry currents of 25 A and 15 A in the same direction. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I₁ = 25 AI₂ = 15 Ad = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

5.Hard

In a velocity selector, crossed fields E = 4 × 10⁴ V/m and B = 0.05 T let only ions of one speed pass straight through. Find that speed v.

E = 4 × 10⁴ V/mB₁ = 0.05 T

v = m/s

6.Hard

A short coil of 50 turns is wound tightly round the middle of a long solenoid of 1500 turns, length 50 cm and diameter 3 cm. The current in the solenoid changes at 10 A/s. Find the emf ε induced in the short coil.

N₁ = 1500N₂ = 50l = 50 cm⌀ = 3 cmdi/dt = 10 A/sμ₀ = 4π × 10⁻⁷ T·m/A

ε = mV

Answer key

1. B = 314.2 µT
2. B = 1.309 mT
3. r = 62.22 cm
4. B = 26.67 µT
5. v = 800000 m/s
6. ε = 1.332 mV

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