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 10 cm long lies at 90° to a uniform magnetic field of 0.2 T. The magnetic force on it is 0.04 N. Find the current I.

B = 0.2 TF = 0.04 NL = 10 cmθ = 90°

I = A

2.Easy

A solenoid 15 cm long has 2000 turns and carries 3 A. Find the magnetic flux density B inside it, far from the ends.

N = 2000L = 15 cmI = 3 Aμ₀ = 4π × 10⁻⁷ T·m/A

B = mT

3.Medium

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

v: down the pageB: into the page

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

4.Medium

An alpha particle moves at 1 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.8 T. Find the radius r of its circular path.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ Cv = 1 × 10⁵ m/sB = 0.8 T

r = cm

5.Hard

A coil of 50 turns, 8 cm × 25 cm, rotates in a uniform field of 0.25 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 11.11 V?

N = 50A = 8 cm × 25 cmB = 0.25 TE_rms = 11.11 V

n = rpm

6.Hard

A proton passes undeflected through a velocity selector with crossed fields E = 4 × 10⁴ V/m and B₁ = 0.5 T. It then enters a second region with only a magnetic field B₂ = 0.8 T, at right angles. Find the radius r of its path there.

E = 4 × 10⁴ V/mB₁ = 0.5 TB₂ = 0.8 Tm = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ C

r = cm

Answer key

1. I = 2 A
2. B = 50.27 mT
3. to the right
4. r = 0.2592 cm
5. n = 600.2 rpm
6. r = 0.1044 cm

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