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

The magnetic flux density 2.5 cm from a long straight wire is 400 µT. Find the current I in the wire.

B = 400 µTr = 2.5 cmμ₀ = 4π × 10⁻⁷ T·m/A

I = A

2.Easy

A straight wire 80 cm long carries 3 A at an angle of 90° to a uniform magnetic field of 0.5 T. Find the magnitude of the force F on the wire.

B = 0.5 TI = 3 AL = 80 cmθ = 90°

F = N

3.Medium

A wire carries a current to the left through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on the wire.

I: to the leftB: out of the page

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

4.Medium

A coil of 10 turns has an area of 100 cm². The coil sits in a uniform field of 0.3 T perpendicular to its plane, and the field is switched off in 500 ms. Find the average induced emf ε.

N = 10A = 100 cm²B = 0.3 TΔt = 500 ms

ε = mV

5.Hard

A coil of 50 turns, 10 cm × 5 cm, rotates in a uniform field of 0.1 T about an axis perpendicular to the field. At what speed n (in revolutions per minute) must it turn to give an rms emf of 0.5554 V?

N = 50A = 10 cm × 5 cmB = 0.1 TE_rms = 0.5554 V

n = rpm

6.Hard

A coil of 50 turns, 12 cm × 25 cm, rotates at 600 rpm in a uniform field of 0.25 T about an axis perpendicular to the field. Find the rms value E_rms of the emf.

N = 50A = 12 cm × 25 cmB = 0.25 Tn = 600 rpm

E_rms = V

Answer key

1. I = 50 A
2. F = 1.2 N
3. up the page
4. ε = 60 mV
5. n = 300 rpm
6. E_rms = 16.66 V

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