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 = 3 AR = 8 cmB = ?N = 20

A flat circular coil of 20 turns and radius 8 cm carries a current of 3 A. Find the magnetic flux density B at its centre.

N = 20I = 3 AR = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
I = 5 AR = 12 cmB = ?N = 5

A flat circular coil of 5 turns and radius 12 cm carries a current of 5 A. Find the magnetic flux density B at its centre.

N = 5I = 5 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
R = 4 Ωv = 3 m/sL = 50 cmB = 0.1 T

A metal rod 50 cm long slides at 3 m/s along two rails in a uniform field of 0.1 T into the page. The rails are joined by a resistor of 4 Ω; the rod and rails have negligible resistance. Find the power P dissipated in the resistor.

B = 0.1 TL = 50 cmv = 3 m/sR = 4 Ω
P = mW
4.Medium
dB/dt > 0I = ?

A circular loop lies in a uniform magnetic field pointing into the page. The field strength is increasing. 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
L = 500 mH2 → 4 A

The current in a 500 mH inductor changes steadily from 2 A to 4 A in 20 ms. Find the magnitude of the self-induced emf ε.

L = 500 mH2 A → 4 AΔt = 20 ms
ε = V
6.Hard
V = 2000 VB = 0.2 Tr = ?

A deuteron starts from rest, is accelerated through a potential difference of 2000 V and then enters a uniform magnetic field of 0.2 T at right angles. Find the radius r of its path in the field.

m = 3.344 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 2000 VB = 0.2 T
r = cm

Answer key

  1. 1. B = 471.2 µT
  2. 2. B = 130.9 µT
  3. 3. P = 5.625 mW
  4. 4. counterclockwise
  5. 5. ε = 50 V
  6. 6. r = 4.569 cm

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