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 = 31.42 mTI = ?L = 40 cmN = 2000

A solenoid 40 cm long has 2000 turns. Which current I gives a magnetic flux density of 31.42 mT inside it?

N = 2000L = 40 cmB = 31.42 mTμ₀ = 4π × 10⁻⁷ T·m/A
I = A
2.Easy
I = 10 APr = 5 cmB = ?

A long straight wire carries a current of 10 A. Find the magnetic flux density B at point P, 5 cm from the wire.

I = 10 Ar = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
nBA = 40 cm², N = 200B: 0 → 0.6 T

A coil of 200 turns has an area of 40 cm². A uniform field perpendicular to the coil rises steadily from 0 T to 0.6 T in 20 ms. Find the average induced emf ε.

N = 200A = 40 cm²B: 0 T → 0.6 TΔt = 20 ms
ε = V
4.Medium
nBA = 100 cm², N = 10B = 0.4 T

A coil of 10 turns has an area of 100 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.4 T, which is perpendicular to its plane, in 250 ms. Find the average induced emf ε.

N = 10A = 100 cm²B = 0.4 TΔt = 250 ms
ε = mV
5.Hard
L = 200 mH2 → 3.5 A

The current in a 200 mH inductor changes steadily from 2 A to 3.5 A in 5 ms. Find the magnitude of the self-induced emf ε.

L = 200 mH2 A → 3.5 AΔt = 5 ms
ε = V
6.Hard
Bn = 3600 rpm8 cm × 25 cmN = 250B = 0.2 T

A coil of 250 turns, 8 cm × 25 cm, rotates at 3600 rpm in a uniform field of 0.2 T about an axis perpendicular to the field. Find the peak emf E0.

N = 250A = 8 cm × 25 cmB = 0.2 Tn = 3600 rpm
E0 = V

Answer key

  1. 1. I = 5.001 A
  2. 2. B = 40 µT
  3. 3. ε = 24 V
  4. 4. ε = 320 mV
  5. 5. ε = 60 V
  6. 6. E0 = 377 V

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