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
B0.5 T1 A90°L = 50 cm

A straight wire 50 cm long carries 1 A at an angle of 90° to a uniform magnetic field of 0.5 T. Find the magnitude of the force F on the wire.

B = 0.5 TI = 1 AL = 50 cmθ = 90°
F = N
2.Easy
I = 1.5 AR = 6 cmB = ?N = 5

A flat circular coil of 5 turns and radius 6 cm carries a current of 1.5 A. Find the magnetic flux density B at its centre.

N = 5I = 1.5 AR = 6 cmμ₀ = 4π × 10⁻⁷ T·m/A
B = µT
3.Medium
nBA = 150 cm², N = 10B = 0.5 T

A coil of 10 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 500 ms. Find the average induced emf ε.

N = 10A = 150 cm²B = 0.5 TΔt = 500 ms
ε = mV
4.Medium
−v = 3 × 10⁶ m/sr = 0.6823 cmB = ?

An electron moving at 3 × 10⁶ m/s enters a uniform magnetic field at right angles and moves on a circle of radius 0.6823 cm. Find the magnetic flux density B.

m = 9.109 × 10⁻³¹ kg|q| = 1.602 × 10⁻¹⁹ Cv = 3 × 10⁶ m/sr = 0.6823 cm
B = mT
5.Hard
E = 5 × 10⁴ V/m, B1​ = 0.25 TB2​ = 0.4 Tr = ?

A proton passes undeflected through a velocity selector with crossed fields E = 5 × 10⁴ V/m and B₁ = 0.25 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 = 5 × 10⁴ V/mB1 = 0.25 TB2 = 0.4 Tm = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ C
r = cm
6.Hard
V = 500 VB = 0.4 Tr = ?

A proton starts from rest, is accelerated through a potential difference of 500 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 = 1.673 × 10⁻²⁷ kg|q| = 1.602 × 10⁻¹⁹ CV = 500 VB = 0.4 T
r = cm

Answer key

  1. 1. F = 0.25 N
  2. 2. B = 78.54 µT
  3. 3. ε = 300 mV
  4. 4. B = 2.5 mT
  5. 5. r = 0.5222 cm
  6. 6. r = 0.8079 cm

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