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
++1 µC−−6 µCr = 4 cm

Two point charges of +1 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 = +1 µCq2 = −6 µCr = 4 cm
F = N
2.Easy
−−4 µC−−2 µCr = 2 cm

Two point charges of −4 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 = −4 µCq2 = −2 µCr = 2 cm
F = N
3.Medium
++2 µC−−6 µCP10 cm

A charge of +2 µC and a charge of −6 µC are 10 cm apart. Point P lies on the line between them, 4 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +2 µCq2 = −6 µCr1 = 4 cmr2 = 6 cm
E = N/C
4.Medium
++1 µC++5 µC−−4 µC4 cm + 6 cm

Three point charges lie on a straight line: +1 µC on the left, −4 µC on the right 10 cm away, and +5 µC between them, 4 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 = +1 µCqR = −4 µCqM = +5 µCrL = 4 cmrR = 6 cm
F = N
5.Hard
10 cm6 cm+q1​ = +1 µC+q3​ = +8 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 8 µC is at the right-angle corner, q₁ = 1 µC is 10 cm from it along one side and q₂ = 1 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 1 µCq2 = 1 µCq3 = 8 µCr13 = 10 cmr23 = 6 cm
F = N
6.Hard
3 cm5 cm+q1​ = +10 µC+q3​ = +1 µC+q2​ = +6 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 10 µC is 3 cm from it along one side and q₂ = 6 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 6 µCq3 = 1 µCr13 = 3 cmr23 = 5 cm
F = N

Answer key

  1. 1. F = 33.71 N
  2. 2. F = 179.8 N
  3. 3. E = 2.622 × 10⁷ N/C
  4. 4. F = 78.04 N
  5. 5. F = 21.23 N
  6. 6. F = 102.2 N

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