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 = 3 cmB = ?N = 10

A flat circular coil of 10 turns and radius 3 cm carries a current of 1 A. Find the magnetic flux density B at its centre.

N = 10I = 1 AR = 3 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
2.Easy
I = 3 AR = 5 cmB = ?N = 10

A flat circular coil of 10 turns and radius 5 cm carries a current of 3 A. Find the magnetic flux density B at its centre.

N = 10I = 3 AR = 5 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
nBA = 40 cm², N = 200B = 0.8 T

A coil of 200 turns has an area of 40 cm². The coil sits in a uniform field of 0.8 T perpendicular to its plane, and the field is switched off in 20 ms. Find the average induced emf ε.

N = 200A = 40 cm²B = 0.8 TΔt = 20 ms
ε = V
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
V = 2500 VB = 0.4 Tr = ?

An alpha particle starts from rest, is accelerated through a potential difference of 2500 V and then enters a uniform magnetic field of 0.4 T at right angles. Find the radius r of its path in the field.

m = 6.645 × 10⁻²⁷ kg|q| = 3.204 × 10⁻¹⁹ CV = 2500 VB = 0.4 T
r = cm
6.Hard
Bn = ?20 cm × 15 cmN = 200B = 0.2 T

A coil of 200 turns, 20 cm × 15 cm, rotates in a uniform field of 0.2 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 266.6 V?

N = 200A = 20 cm × 15 cmB = 0.2 TErms = 266.6 V
n = rpm

Answer key

  1. 1. B = 209.4 µT
  2. 2. B = 377 µT
  3. 3. ε = 32 V
  4. 4. counterclockwise
  5. 5. r = 2.546 cm
  6. 6. n = 3000 rpm

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