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 = 2 AR = 3 cmB = ?N = 100

A flat circular coil of 100 turns and radius 3 cm carries a current of 2 A. Find the magnetic flux density B at its centre.

N = 100I = 2 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
2.Easy
I = 4 AR = 3 cmB = ?N = 20

A flat circular coil of 20 turns and radius 3 cm carries a current of 4 A. Find the magnetic flux density B at its centre.

N = 20I = 4 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = mT
3.Medium
nBA = 150 cm², N = 250B = 0.3 T

A coil of 250 turns has an area of 150 cm². The coil sits in a uniform field of 0.3 T perpendicular to its plane, and the field is switched off in 50 ms. Find the average induced emf ε.

N = 250A = 150 cm²B = 0.3 TΔt = 50 ms
ε = V
4.Medium
−vBF = ?

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

v: up the pageB: out of the page
  1. 1up the page
  2. 2to the right
  3. 3down the page
  4. 4to the left
5.Hard
E = 1 × 10⁴ V/m, B1​ = 0.5 TB2​ = 1 Tr = ?

A deuteron passes undeflected through a velocity selector with crossed fields E = 1 × 10⁴ V/m and B₁ = 0.5 T. It then enters a second region with only a magnetic field B₂ = 1 T, at right angles. Find the radius r of its path there.

E = 1 × 10⁴ V/mB1 = 0.5 TB2 = 1 Tm = 3.344 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ C
r = cm
6.Hard
Bn = ?20 cm × 15 cmN = 150B = 0.1 T

A coil of 150 turns, 20 cm × 15 cm, rotates in a uniform field of 0.1 T about an axis perpendicular to the field. At what speed n (in revolutions per minute) must it turn to give an rms emf of 29.99 V?

N = 150A = 20 cm × 15 cmB = 0.1 TErms = 29.99 V
n = rpm

Answer key

  1. 1. B = 4.189 mT
  2. 2. B = 1.676 mT
  3. 3. ε = 22.5 V
  4. 4. to the left
  5. 5. r = 0.04175 cm
  6. 6. n = 900 rpm

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