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
++10 nCPr = 5 cm

Find the magnitude of the electric field E at a distance of 5 cm from a point charge of +10 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = +10 nCr = 5 cm
E = N/C
2.Easy
−−6 µC−−2 µCr = 10 cm

Two point charges of −6 µC and −2 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 = −2 µCr = 10 cm
F = N
3.Medium
++1 µC−−8 µCP30 cm

A charge of +1 µC and a charge of −8 µC are 30 cm apart. Point P lies on the line between them, 12 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = −8 µCr1 = 12 cmr2 = 18 cm
E = N/C
4.Medium
−−4 µC−−8 µCr = 20 cm

Two identical small metal spheres carry charges of −4 µC and −8 µC. They are touched together and then put back 20 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −4 µCq2 = −8 µCr = 20 cm
F = N
5.Hard
6 cm5 cm+q1​ = +4 µC+q3​ = +6 µC+q2​ = +2 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 4 µC is 6 cm from it along one side and q₂ = 2 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 4 µCq2 = 2 µCq3 = 6 µCr13 = 6 cmr23 = 5 cm
F = N
6.Hard
3 cm5 cm+q1​ = +3 µC+q3​ = +10 µC+q2​ = +3 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 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 = 3 µCq2 = 3 µCq3 = 10 µCr13 = 3 cmr23 = 5 cm
F = N

Answer key

  1. 1. E = 35960 N/C
  2. 2. F = 10.79 N
  3. 3. E = 2.844 × 10⁶ N/C
  4. 4. F = 8.091 N
  5. 5. F = 73.85 N
  6. 6. F = 318.5 N

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