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 = 15 APr = ?B = 20 µT

A long straight wire carries 15 A. At what distance r from the wire is the magnetic flux density 20 µT?

I = 15 AB = 20 µTμ₀ = 4π × 10⁻⁷ T·m/A
r = cm
2.Easy
I = 1 AR = 3 cmB = ?N = 100

A flat circular coil of 100 turns and radius 3 cm carries a current of 1 A. Find the magnetic flux density B at its centre.

N = 100I = 1 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
3.Medium
IBF = ?

A wire carries a current up the page through a uniform magnetic field pointing into the page. Click the direction of the magnetic force on the wire.

I: up the pageB: into the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
dB/dt > 0I = ?

A circular loop lies in a uniform magnetic field pointing out of the page. The field strength is increasing. Click the direction of the induced current in the loop as seen in the drawing.

B: out of the pagedB/dt > 0
  1. 1clockwise
  2. 2counterclockwise
5.Hard
Bn = ?8 cm × 25 cmN = 20B = 0.1 T

A coil of 20 turns, 8 cm × 25 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 10.66 V?

N = 20A = 8 cm × 25 cmB = 0.1 TErms = 10.66 V
n = rpm
6.Hard
E = 4 × 10⁴ V/m, B1​ = 0.05 T

In a velocity selector, crossed fields E = 4 × 10⁴ V/m and B = 0.05 T let only ions of one speed pass straight through. Find that speed v.

E = 4 × 10⁴ V/mB1 = 0.05 T
v = m/s

Answer key

  1. 1. r = 15 cm
  2. 2. B = 2.094 mT
  3. 3. to the left
  4. 4. clockwise
  5. 5. n = 3599 rpm
  6. 6. v = 800000 m/s

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