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++6 µCr = 10 cm

Two point charges of +6 µC and +6 µC are 10 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +6 µCq2 = +6 µCr = 10 cm
F = N
2.Easy
−−200 nCPr = 40 cm

Find the magnitude of the electric field E at a distance of 40 cm from a point charge of −200 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = −200 nCr = 40 cm
E = N/C
3.Medium
++3 µC−−4 µCP20 cm

A charge of +3 µC and a charge of −4 µC are 20 cm apart. Point P lies on the line between them, 8 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +3 µCq2 = −4 µCr1 = 8 cmr2 = 12 cm
E = N/C
4.Medium
++3 µC++8 µC−−10 µC22.5 cm + 7.5 cm

Three point charges lie on a straight line: +3 µC on the left, −10 µC on the right 30 cm away, and +8 µC between them, 22.5 cm from the left charge. Find the magnitude of the net electric force F on the middle charge. Use k = 8.99 × 10⁹ N·m²/C².

qL = +3 µCqR = −10 µCqM = +8 µCrL = 22.5 cmrR = 7.5 cm
F = N
5.Hard
3 cm5 cm+q1​ = +10 µC+q3​ = +2 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 10 µC is 3 cm from it along one side and q₂ = 3 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 3 µCq3 = 2 µCr13 = 3 cmr23 = 5 cm
F = N
6.Hard
6 cm8 cm+q1​ = +2 µC+q3​ = +6 µC+q2​ = +8 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 2 µC is 6 cm from it along one side and q₂ = 8 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 8 µCq3 = 6 µCr13 = 6 cmr23 = 8 cm
F = N

Answer key

  1. 1. F = 32.36 N
  2. 2. E = 11238 N/C
  3. 3. E = 6.711 × 10⁶ N/C
  4. 4. F = 132.1 N
  5. 5. F = 200.9 N
  6. 6. F = 73.78 N

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