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 long straight wire carries a current of 4 A. Find the magnetic flux density B at point P, 1 cm from the wire.

I = 4 Ar = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A

B = µT

2.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

3.Medium

A proton moves at 2 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.8 T. Find the radius r of its circular path.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 2 × 10⁶ m/sB = 0.8 T

r = cm

4.Medium

A proton moves at 2 × 10⁶ m/s perpendicular to a uniform magnetic field of 0.25 T. Find the radius r of its circular path.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ Cv = 2 × 10⁶ m/sB = 0.25 T

r = cm

5.Hard

A coil of 20 turns, 20 cm × 10 cm, rotates at 1200 rpm in a uniform field of 0.3 T about an axis perpendicular to the field. Find the rms value E_rms of the emf.

N = 20A = 20 cm × 10 cmB = 0.3 Tn = 1200 rpm

E_rms = V

6.Hard

An alpha particle starts from rest, is accelerated through a potential difference of 5000 V and then enters a uniform magnetic field of 0.4 T at right angles. Find the radius r of its path in the field.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ CV = 5000 VB = 0.4 T

r = cm

Answer key

1. B = 80 µT
2. I = 50 A
3. r = 2.611 cm
4. r = 8.355 cm
5. E_rms = 10.66 V
6. r = 3.6 cm

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