Coulomb’s law & electric fields worksheet with answers

Free printable Coulomb’s law & electric fields 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
−−6 µC++8 µCr = 8 cm

Two point charges of −6 µC and +8 µC are 8 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −6 µCq2 = +8 µCr = 8 cm
F = N
2.Easy
+ + + + + +− − − − − −e⁻E = 2700 N/C

An electron (charge −1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg) is in a uniform electric field of 2700 N/C. Ignoring gravity, find the magnitude of its acceleration a.

E = 2700 N/C|q| = 1.602 × 10⁻¹⁹ Cm = 9.109 × 10⁻³¹ kg
a = m/s²
3.Medium
++1 µC++6 µCP10 cm

A charge of +1 µC and a charge of +6 µC are 10 cm apart. Point P lies on the line between them, 7.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = +6 µCr1 = 7.5 cmr2 = 2.5 cm
E = N/C
4.Medium
++2 µC−−3 µCr = 20 cm

Two identical small metal spheres carry charges of +2 µC and −3 µC. They are touched together and then put back 20 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = −3 µCr = 20 cm
F = N
5.Hard
+ + + + + +− − − − − −e⁻3 × 10⁷ m/s4 cmE = 3400 N/C

An electron enters the uniform field between two parallel plates moving parallel to them at 3 × 10⁷ m/s. The plates are 4 cm long and the field between them is 3400 N/C. Electron charge 1.602 × 10⁻¹⁹ C, mass 9.109 × 10⁻³¹ kg; ignore gravity. How far y is it deflected sideways when it leaves the plates? Give the answer in mm.

v₀ = 3 × 10⁷ m/sL = 4 cmE = 3400 N/Ce = 1.602 × 10⁻¹⁹ Cme = 9.109 × 10⁻³¹ kg
y = mm
6.Hard
L = 80 cm20°qq

Two identical small balls, each of mass 1 g, hang from the same point on insulating threads 80 cm long. They are given equal charges and each thread settles at 20° from the vertical. Use g = 9.81 m/s². Find the charge q on each ball in nC. Use k = 8.99 × 10⁹ N·m²/C².

m = 1 gL = 80 cmθ = 20°g = 9.81 m/s²
q = nC

Answer key

  1. 1. F = 67.42 N
  2. 2. a = 4.748 × 10¹⁴ m/s²
  3. 3. E = 8.471 × 10⁷ N/C
  4. 4. F = 0.05619 N
  5. 5. y = 0.5315 mm
  6. 6. q = 344.9 nC

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