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
−−2 µC−−10 µCr = 6 cm

Two point charges of −2 µC and −10 µC are 6 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −2 µCq2 = −10 µCr = 6 cm
F = N
2.Easy
−−8 µC++1 µCr = 10 cm

Two point charges of −8 µC and +1 µC are 10 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = +1 µCr = 10 cm
F = N
3.Medium
−−6 µC++1 µC−−2 µC16 cm + 24 cm

Three point charges lie on a straight line: −6 µC on the left, −2 µC on the right 40 cm away, and +1 µC between them, 16 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 = −6 µCqR = −2 µCqM = +1 µCrL = 16 cmrR = 24 cm
F = N
4.Medium
++6 µC++3 µCP20 cm

A charge of +6 µC and a charge of +3 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 = +6 µCq2 = +3 µCr1 = 8 cmr2 = 12 cm
E = N/C
5.Hard
5 cm5 cm+q1​ = +3 µC+q3​ = +3 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 3 µC is 5 cm from it along one side and q₂ = 4 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 3 µCq2 = 4 µCq3 = 3 µCr13 = 5 cmr23 = 5 cm
F = N
6.Hard
5 cm5 cm+q1​ = +3 µC+q3​ = +10 µC+q2​ = +10 µC

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

q1 = 3 µCq2 = 10 µCq3 = 10 µCr13 = 5 cmr23 = 5 cm
F = N

Answer key

  1. 1. F = 49.94 N
  2. 2. F = 7.192 N
  3. 3. F = 1.795 N
  4. 4. E = 6.555 × 10⁶ N/C
  5. 5. F = 53.94 N
  6. 6. F = 375.4 N

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