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 = ?I = 0.5 AL = 25 cmN = 250

A solenoid 25 cm long has 250 turns and carries 0.5 A. Find the magnetic flux density B inside it, far from the ends.

N = 250L = 25 cmI = 0.5 Aμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
2.Easy
−v = 4 × 10⁵ m/sB = 0.02 T

An electron moves at 4 × 10⁵ m/s perpendicular to a uniform magnetic field of 0.02 T. Find the magnitude of the magnetic force F on it.

|q| = 1.602 × 10⁻¹⁹ Cv = 4 × 10⁵ m/sB = 0.02 Tθ = 90°
F = fN
3.Medium
R = 4 Ωv = 2.5 m/sL = 60 cmB = 0.6 T

A metal rod 60 cm long slides at 2.5 m/s along two rails in a uniform field of 0.6 T into the page. The rails are joined by a resistor of 4 Ω; the rod and rails have negligible resistance. Find the current I.

B = 0.6 TL = 60 cmv = 2.5 m/sR = 4 Ω
I = mA
4.Medium
vI = ?

A square loop moves to the right into a region with a uniform magnetic field pointing into the page. Click the direction of the induced current in the loop as seen in the drawing, while the loop is entering the field.

B: into the pageentering the field
  1. 1clockwise
  2. 2counterclockwise
5.Hard
l = 25 cmN = 200, ⌀ 4 cm

A long air-core solenoid has 200 turns, a length of 25 cm and a diameter of 4 cm. Find its self-inductance L.

N = 200l = 25 cm⌀ = 4 cmμ₀ = 4π × 10⁻⁷ T·m/A
L = µH
6.Hard
V = 10000 VB = 0.5 Tr = ?

A proton starts from rest, is accelerated through a potential difference of 10000 V and then enters a uniform magnetic field of 0.5 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 = 10000 VB = 0.5 T
r = cm

Answer key

  1. 1. B = 0.6283 mT
  2. 2. F = 1.282 fN
  3. 3. I = 225 mA
  4. 4. counterclockwise
  5. 5. L = 252.7 µH
  6. 6. r = 2.89 cm

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