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
B0.3 TI = ?90°L = 50 cm

A straight wire 50 cm long lies at 90° to a uniform magnetic field of 0.3 T. The magnetic force on it is 1.5 N. Find the current I.

B = 0.3 TF = 1.5 NL = 50 cmθ = 90°
I = A
2.Easy
nB12 cm × 10 cmB = 1.2 T

A rectangular loop of 12 cm by 10 cm lies in a uniform magnetic field of 1.2 T. The field makes an angle of 0° with the normal of the loop. Find the magnetic flux Φ through the loop.

B = 1.2 TA = 12 cm × 10 cm0° to the normal
Φ = mWb
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
15 A12 Ad = 8 cm

Two long parallel wires 8 cm apart carry currents of 15 A and 12 A in opposite directions. Find the force per metre of length F/L between them.

I1 = 15 AI2 = 12 Ad = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
5.Hard
L1​ = 50 mH20 A/sL2​ = 50 mHk = 0.9ε = ?

Two coils with self-inductances of 50 mH and 50 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 = 50 mHL2 = 50 mHk = 0.9di/dt = 20 A/s
ε = V
6.Hard
E = 8 × 10⁴ V/m, B1​ = 0.4 T

In a velocity selector, crossed fields E = 8 × 10⁴ V/m and B = 0.4 T let only ions of one speed pass straight through. Find that speed v.

E = 8 × 10⁴ V/mB1 = 0.4 T
v = m/s

Answer key

  1. 1. I = 10 A
  2. 2. Φ = 14.4 mWb
  3. 3. to the right
  4. 4. F/L = 450 µN/m
  5. 5. ε = 0.9 V
  6. 6. v = 200000 m/s

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