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 = 15.71 mTI = 2.5 AL = 40 cmN = ?

A solenoid 40 cm long carries 2.5 A. How many turns N must it have for a flux density of 15.71 mT inside?

I = 2.5 AL = 40 cmB = 15.71 mTμ₀ = 4π × 10⁻⁷ T·m/A
N =
2.Easy
nB37°10 cm × 10 cmB = 0.3 T

A rectangular loop of 10 cm by 10 cm lies in a uniform magnetic field of 0.3 T. The field lines make an angle of 53° with the plane of the loop. Find the magnetic flux Φ through the loop.

B = 0.3 TA = 10 cm × 10 cm53° to the plane
Φ = mWb
3.Medium
15 A30 Ad = 12 cm

Two long parallel wires 12 cm apart carry currents of 15 A and 30 A in the same direction. Find the force per metre of length F/L between them.

I1 = 15 AI2 = 30 Ad = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
F/L = µN/m
4.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
5.Hard
l = 40 cmN = 1500, ⌀ 1 cm

A long air-core solenoid has 1500 turns, a length of 40 cm and a diameter of 1 cm. Find its self-inductance L.

N = 1500l = 40 cm⌀ = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = µH
6.Hard
L = 500 mH1 → 5 A

The current in a 500 mH inductor changes steadily from 1 A to 5 A in 20 ms. Find the magnitude of the self-induced emf ε.

L = 500 mH1 A → 5 AΔt = 20 ms
ε = V

Answer key

  1. 1. N = 2000
  2. 2. Φ = 2.396 mWb
  3. 3. F/L = 750 µN/m
  4. 4. to the right
  5. 5. L = 555.2 µH
  6. 6. ε = 100 V

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