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 = 1 AR = 8 cmB = ?N = 25

A flat circular coil of 25 turns and radius 8 cm carries a current of 1 A. Find the magnetic flux density B at its centre.

N = 25I = 1 AR = 8 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
B = ?I = 2 AL = 20 cmN = 800

A solenoid 20 cm long has 800 turns and carries 2 A. Find the magnetic flux density B inside it, far from the ends.

N = 800L = 20 cmI = 2 Aμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
3.Medium
+vBF = ?

A proton moves to the left through a uniform magnetic field pointing into the page. Click the direction of the magnetic force on it.

v: to the leftB: into the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
4.Medium
R = 10 Ωv = 6 m/sL = 60 cmB = 0.6 T

A metal rod 60 cm long slides at 6 m/s along two rails in a uniform field of 0.6 T into the page. Find the induced emf ε between its ends.

B = 0.6 TL = 60 cmv = 6 m/s
ε = V
5.Hard
V = 500 VB = 0.2 Tr = ?

A proton starts from rest, is accelerated through a potential difference of 500 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 = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 500 VB = 0.2 T
r = cm
6.Hard
I = 2.5 Al = 20 cmN = 1500, ⌀ 5 cm

A long air-core solenoid has 1500 turns, a length of 20 cm and a diameter of 5 cm. Find the energy W stored in its magnetic field when it carries 2.5 A.

N = 1500l = 20 cm⌀ = 5 cmI = 2.5 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = mJ

Answer key

  1. 1. B = 196.3 µT
  2. 2. B = 10.05 mT
  3. 3. down the page
  4. 4. ε = 2.16 V
  5. 5. r = 1.616 cm
  6. 6. W = 86.74 mJ

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