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.

New worksheetPractise online with hints

For teachers: free to print, copy and use in class. Every new worksheet has new values and its own answer key. A link to ExamProblems on your course page is appreciated.

Name: ____________________   Date: ____________

1.Easy
I = 12 APr = 4 cmB = ?

A long straight wire carries a current of 12 A. Find the magnetic flux density B at point P, 4 cm from the wire.

I = 12 Ar = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
+v = 6 × 10⁵ m/sB = 0.1 T

A proton moves at 6 × 10⁵ m/s at an angle of 45° to a uniform magnetic field of 0.1 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 6 × 10⁵ m/sB = 0.1 Tθ = 45°
F = fN
3.Medium
+vBF = ?

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
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
R = 1 Ωv = 1 m/sL = 30 cmB = 0.6 T

A metal rod 30 cm long slides at 1 m/s along two rails in a uniform field of 0.6 T into the page. The rails are joined by a resistor of 1 Ω; the rod and rails have negligible resistance. Find the force F needed to keep the rod moving at constant speed (no friction).

B = 0.6 TL = 30 cmv = 1 m/sR = 1 Ω
F = mN
5.Hard
L1​ = 80 mH200 A/sL2​ = 5 mHk = 0.9ε = ?

Two coils with self-inductances of 80 mH and 5 mH have a coupling coefficient of 0.9. The current in the first coil changes at 200 A/s. Find the emf ε induced in the second coil.

L1 = 80 mHL2 = 5 mHk = 0.9di/dt = 200 A/s
ε = V
6.Hard
Bn = 1200 rpm10 cm × 10 cmN = 100B = 0.05 T

A coil of 100 turns, 10 cm × 10 cm, rotates at 1200 rpm in a uniform field of 0.05 T about an axis perpendicular to the field. Find the rms value Erms of the emf.

N = 100A = 10 cm × 10 cmB = 0.05 Tn = 1200 rpm
Erms = V

Answer key

  1. 1. B = 60 µT
  2. 2. F = 6.797 fN
  3. 3. to the right
  4. 4. F = 32.4 mN
  5. 5. ε = 3.6 V
  6. 6. Erms = 4.443 V

Full step-by-step solutions: practise this topic on examproblems.com.