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 100 cm long lies at 90° to a uniform magnetic field of 0.4 T. The magnetic force on it is 2.4 N. Find the current I.

B = 0.4 TF = 2.4 NL = 100 cmθ = 90°

I = A

2.Easy

A solenoid 30 cm long has 1000 turns. Which current I gives a magnetic flux density of 16.76 mT inside it?

N = 1000L = 30 cmB = 16.76 mTμ₀ = 4π × 10⁻⁷ T·m/A

I = A

3.Medium

A metal rod 20 cm long slides at 5 m/s along two rails in a uniform field of 0.2 T into the page. The rails are joined by a resistor of 4 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.2 TL = 20 cmv = 5 m/sR = 4 Ω

P = mW

4.Medium

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

v: up the pageB: out of the page

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

5.Hard

A coil of 20 turns, 15 cm × 5 cm, rotates at 1800 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 = 20A = 15 cm × 5 cmB = 0.5 Tn = 1800 rpm

E_rms = V

6.Hard

A long air-core solenoid has 300 turns, a length of 20 cm and a diameter of 4 cm. Find its self-inductance L.

N = 300l = 20 cm⌀ = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A

L = µH

Answer key

1. I = 6 A
2. I = 4.001 A
3. P = 10 mW
4. to the right
5. E_rms = 9.996 V
6. L = 710.6 µH

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