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
I = ?Pr = 3 cmB = 266.7 µT

The magnetic flux density 3 cm from a long straight wire is 266.7 µT. Find the current I in the wire.

B = 266.7 µTr = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
I = A
2.Easy
I = 5 APr = 10 cmB = ?

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

I = 5 Ar = 10 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
nBA = 10 cm², N = 25B: 0.1 → 0.4 T

A coil of 25 turns, area 10 cm² and resistance 10 Ω forms a closed circuit. A uniform field perpendicular to the coil rises steadily from 0.1 T to 0.4 T in 20 ms. Find the average induced current I.

N = 25A = 10 cm²B: 0.1 T → 0.4 TΔt = 20 msR = 10 Ω
I = mA
4.Medium
−v = 8 × 10⁶ m/sB = 5 mT

An electron moves on a circle in a uniform magnetic field of 5 mT. Find the time T it takes for one revolution.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ CB = 5 mT
T = ns
5.Hard
V = 2000 VB = 0.25 Tr = ?

A proton starts from rest, is accelerated through a potential difference of 2000 V and then enters a uniform magnetic field of 0.25 T at right angles. Find the radius r of its path in the field.

m = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 2000 VB = 0.25 T
r = cm
6.Hard
l = 20 cmN = 400, ⌀ 1 cm

A long air-core solenoid has 400 turns, a length of 20 cm and a diameter of 1 cm. Find its self-inductance L.

N = 400l = 20 cm⌀ = 1 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = µH

Answer key

  1. 1. I = 40 A
  2. 2. B = 10 µT
  3. 3. I = 37.5 mA
  4. 4. T = 7.145 ns
  5. 5. r = 2.585 cm
  6. 6. L = 78.96 µH

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