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
−−8 µC−−6 µCr = 4 cm

Two point charges of −8 µC and −6 µC are 4 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = −6 µCr = 4 cm
F = N
2.Easy
−−3 µC−−1 µCr = 10 cm

Two point charges of −3 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 = −3 µCq2 = −1 µCr = 10 cm
F = N
3.Medium
−−4 µC−−4 µC++4 µC20 cm + 20 cm

Three point charges lie on a straight line: −4 µC on the left, +4 µC on the right 40 cm away, and −4 µC between them, 20 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 = −4 µCqR = +4 µCqM = −4 µCrL = 20 cmrR = 20 cm
F = N
4.Medium
++5 µC−−2 µCP50 cm

A charge of +5 µC and a charge of −2 µC are 50 cm apart. Point P lies on the line between them, 25 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = −2 µCr1 = 25 cmr2 = 25 cm
E = N/C
5.Hard
4 cm4 cm+q1​ = +4 µC+q3​ = +1 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 4 µC is 4 cm from it along one side and q₂ = 1 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 4 µCq2 = 1 µCq3 = 1 µCr13 = 4 cmr23 = 4 cm
F = N
6.Hard
5 cm4 cm+q1​ = +8 µC+q3​ = +4 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 8 µC is 5 cm from it along one side and q₂ = 3 µC is 4 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 3 µCq3 = 4 µCr13 = 5 cmr23 = 4 cm
F = N

Answer key

  1. 1. F = 269.7 N
  2. 2. F = 2.697 N
  3. 3. F = 7.192 N
  4. 4. E = 1.007 × 10⁶ N/C
  5. 5. F = 23.17 N
  6. 6. F = 133.4 N

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