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 µCPr = 2 cm

Find the magnitude of the electric field E at a distance of 2 cm from a point charge of −6 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = −6 µCr = 2 cm
E = N/C
2.Easy
−−10 µC−−2 µCr = 2 cm

Two point charges of −10 µC and −2 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −10 µCq2 = −2 µCr = 2 cm
F = N
3.Medium
++3 µC−−10 µCP10 cm

A charge of +3 µC and a charge of −10 µC are 10 cm apart. Point P lies on the line between them, 6 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +3 µCq2 = −10 µCr1 = 6 cmr2 = 4 cm
E = N/C
4.Medium
++6 µC++6 µCP30 cm

A charge of +6 µC and a charge of +6 µC are 30 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 = +6 µCq2 = +6 µCr1 = 7.5 cmr2 = 22.5 cm
E = N/C
5.Hard
6 cm5 cm+q1​ = +2 µC+q3​ = +2 µC+q2​ = +2 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 2 µC is 6 cm from it along one side and q₂ = 2 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 2 µCq3 = 2 µCr13 = 6 cmr23 = 5 cm
F = N
6.Hard
L = 50 cm8°qq

Two identical small balls, each of mass 2 g, hang from the same point on insulating threads 50 cm long. They are given equal charges and each thread settles at 8° 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 = 2 gL = 50 cmθ = 8°g = 9.81 m/s²
q = nC

Answer key

  1. 1. E = 1.349 × 10⁸ N/C
  2. 2. F = 449.5 N
  3. 3. E = 6.368 × 10⁷ N/C
  4. 4. E = 8.524 × 10⁶ N/C
  5. 5. F = 17.51 N
  6. 6. q = 77.08 nC

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