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
nB12 cm × 20 cmB = 0.5 T

A rectangular loop of 12 cm by 20 cm lies in a uniform magnetic field of 0.5 T. The field makes an angle of 0° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 0.5 TA = 12 cm × 20 cm0° to the normal
Φ = mWb
2.Easy
I = 3 AR = 15 cmB = ?N = 25

A flat circular coil of 25 turns and radius 15 cm carries a current of 3 A. Find the magnetic flux density B at its centre.

N = 25I = 3 AR = 15 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
IBF = ?

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

I: down the pageB: into the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
R = 8 Ωv = 8 m/sL = 50 cmB = 0.8 T

A metal rod 50 cm long slides at 8 m/s along two rails in a uniform field of 0.8 T into the page. The rails are joined by a resistor of 8 Ω; the rod and rails have negligible resistance. Find the current I.

B = 0.8 TL = 50 cmv = 8 m/sR = 8 Ω
I = mA
5.Hard
N1​ = 1000, l = 40 cm20 A/sN2​ = 200Mε = ?

A short coil of 200 turns is wound tightly round the middle of a long solenoid of 1000 turns, length 40 cm and diameter 5 cm. The current in the solenoid changes at 20 A/s. Find the emf ε induced in the short coil.

N1 = 1000N2 = 200l = 40 cm⌀ = 5 cmdi/dt = 20 A/sμ₀ = 4π × 10⁻⁷ T·m/A
ε = mV
6.Hard
l = 15 cmN = 1500, ⌀ 1 cm

A long air-core solenoid has 1500 turns, a length of 15 cm and a diameter of 1 cm. Find its self-inductance L.

N = 1500l = 15 cm⌀ = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = mH

Answer key

  1. 1. Φ = 12 mWb
  2. 2. B = 314.2 µT
  3. 3. to the right
  4. 4. I = 400 mA
  5. 5. ε = 24.67 mV
  6. 6. L = 1.48 mH

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