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
I = 1.5 AR = 4 cmB = ?N = 25

A flat circular coil of 25 turns and radius 4 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 25I = 1.5 AR = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
nB53°5 cm × 10 cmB = 0.05 T

A rectangular loop of 5 cm by 10 cm lies in a uniform magnetic field of 0.05 T. The field makes an angle of 53° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.05 TA = 5 cm × 10 cm53° to the normal
Φ = mWb
3.Medium
10 A5 Ad = 10 cmP

Two long parallel wires 10 cm apart carry currents of 10 A and 5 A in opposite directions. Find the magnitude of the magnetic flux density B at point P, halfway between them.

I1 = 10 AI2 = 5 Ad = 10 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
4.Medium
IBF = ?

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

I: down the pageB: out of the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
5.Hard
Bn = ?5 cm × 15 cmN = 250B = 0.1 T

A coil of 250 turns, 5 cm × 15 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 20.83 V?

N = 250A = 5 cm × 15 cmB = 0.1 TErms = 20.83 V
n = rpm
6.Hard
Bn = 1200 rpm15 cm × 20 cmN = 200B = 0.3 T

A coil of 200 turns, 15 cm × 20 cm, rotates at 1200 rpm in a uniform field of 0.3 T about an axis perpendicular to the field. Find the peak emf E0.

N = 200A = 15 cm × 20 cmB = 0.3 Tn = 1200 rpm
E0 = V

Answer key

  1. 1. B = 589 µT
  2. 2. Φ = 0.1505 mWb
  3. 3. B = 60 µT
  4. 4. to the left
  5. 5. n = 1500 rpm
  6. 6. E0 = 226.2 V

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