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 = 5.027 mTI = 2.5 AL = 25 cmN = ?

A solenoid 25 cm long carries 2.5 A. How many turns N must it have for a flux density of 5.027 mT inside?

I = 2.5 AL = 25 cmB = 5.027 mTμ₀ = 4π × 10⁻⁷ T·m/A
N =
2.Easy
I = 1.5 AR = 12 cmB = ?N = 100

A flat circular coil of 100 turns and radius 12 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 100I = 1.5 AR = 12 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
nBA = 150 cm², N = 20B = 0.5 T

A coil of 20 turns has an area of 150 cm². The coil is turned over (rotated through 180°) in a uniform field of 0.5 T, which is perpendicular to its plane, in 250 ms. Find the average induced emf ε.

N = 20A = 150 cm²B = 0.5 TΔt = 250 ms
ε = V
4.Medium
−vBF = ?

An electron moves down the page through a uniform magnetic field pointing out of the page. Click the direction of the magnetic force on it.

v: down the pageB: out of the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
5.Hard
I = 3 Al = 20 cmN = 1000, ⌀ 2.5 cm

A long air-core solenoid has 1000 turns, a length of 20 cm and a diameter of 2.5 cm. Find the energy W stored in its magnetic field when it carries 3 A.

N = 1000l = 20 cm⌀ = 2.5 cmI = 3 Aμ₀ = 4π × 10⁻⁷ T·m/A
W = mJ
6.Hard
E = 8 × 10⁴ V/m, B1​ = 0.1 TB2​ = 0.4 Tr = ?

A deuteron passes undeflected through a velocity selector with crossed fields E = 8 × 10⁴ V/m and B₁ = 0.1 T. It then enters a second region with only a magnetic field B₂ = 0.4 T, at right angles. Find the radius r of its path there.

E = 8 × 10⁴ V/mB1 = 0.1 TB2 = 0.4 Tm = 3.344 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ C
r = cm

Answer key

  1. 1. N = 400
  2. 2. B = 785.4 µT
  3. 3. ε = 1.2 V
  4. 4. to the right
  5. 5. W = 13.88 mJ
  6. 6. r = 4.175 cm

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