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
B = ?I = 4 AL = 30 cmN = 400

A solenoid 30 cm long has 400 turns and carries 4 A. Find the magnetic flux density B inside it, far from the ends.

N = 400L = 30 cmI = 4 Aμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
2.Easy
B0.5 TI = ?60°L = 15 cm

A straight wire 15 cm long lies at 60° to a uniform magnetic field of 0.5 T. The magnetic force on it is 0.6495 N. Find the current I.

B = 0.5 TF = 0.6495 NL = 15 cmθ = 60°
I = A
3.Medium
IBF = ?

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

I: to the rightB: 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 into the page. The field strength is decreasing. Click the direction of the induced current in the loop as seen in the drawing.

B: into the pagedB/dt < 0
  1. 1clockwise
  2. 2counterclockwise
5.Hard
L1​ = 200 mH20 A/sL2​ = 100 mHk = 0.9ε = ?

Two coils with self-inductances of 200 mH and 100 mH have a coupling coefficient of 0.9. The current in the first coil changes at 20 A/s. Find the emf ε induced in the second coil.

L1 = 200 mHL2 = 100 mHk = 0.9di/dt = 20 A/s
ε = V
6.Hard
E = 1 × 10⁵ V/m, B1​ = 0.5 T

In a velocity selector, crossed fields E = 1 × 10⁵ V/m and B = 0.5 T let only ions of one speed pass straight through. Find that speed v.

E = 1 × 10⁵ V/mB1 = 0.5 T
v = m/s

Answer key

  1. 1. B = 6.702 mT
  2. 2. I = 10 A
  3. 3. up the page
  4. 4. clockwise
  5. 5. ε = 2.546 V
  6. 6. v = 200000 m/s

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