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
−−3 µC−−5 µCr = 5 cm

Two point charges of −3 µC and −5 µC are 5 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −3 µCq2 = −5 µCr = 5 cm
F = N
2.Easy
−−8 µC++10 µCr = 8 cm

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

q1 = −8 µCq2 = +10 µCr = 8 cm
F = N
3.Medium
++5 µC++8 µC−−1 µC30 cm + 10 cm

Three point charges lie on a straight line: +5 µC on the left, −1 µC on the right 40 cm away, and +8 µC between them, 30 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 = +5 µCqR = −1 µCqM = +8 µCrL = 30 cmrR = 10 cm
F = N
4.Medium
++3 µC−−3 µCP40 cm

A charge of +3 µC and a charge of −3 µC are 40 cm apart. Point P lies on the line between them, 10 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +3 µCq2 = −3 µCr1 = 10 cmr2 = 30 cm
E = N/C
5.Hard
3 cm3 cm+q1​ = +4 µC+q3​ = +4 µC+q2​ = +2 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 4 µC is 3 cm from it along one side and q₂ = 2 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 4 µCq2 = 2 µCq3 = 4 µCr13 = 3 cmr23 = 3 cm
F = N
6.Hard
8 cm8 cm+q1​ = +1 µC+q3​ = +3 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 1 µC is 8 cm from it along one side and q₂ = 10 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 1 µCq2 = 10 µCq3 = 3 µCr13 = 8 cmr23 = 8 cm
F = N

Answer key

  1. 1. F = 53.94 N
  2. 2. F = 112.4 N
  3. 3. F = 11.19 N
  4. 4. E = 2.997 × 10⁶ N/C
  5. 5. F = 178.7 N
  6. 6. F = 42.35 N

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