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−−4 µCr = 8 cm

Two point charges of −2 µC and −4 µC are 8 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −2 µCq2 = −4 µCr = 8 cm
F = N
2.Easy
++10 µC−−10 µCr = 10 cm

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

q1 = +10 µCq2 = −10 µCr = 10 cm
F = N
3.Medium
++8 µC++5 µCP20 cm

A charge of +8 µC and a charge of +5 µC are 20 cm apart. Point P lies on the line between them, 15 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +8 µCq2 = +5 µCr1 = 15 cmr2 = 5 cm
E = N/C
4.Medium
−−6 µC−−10 µCr = 20 cm

Two identical small metal spheres carry charges of −6 µC and −10 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 = −6 µCq2 = −10 µCr = 20 cm
F = N
5.Hard
6 cm6 cm+q1​ = +2 µC+q3​ = +6 µC+q2​ = +8 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 2 µC is 6 cm from it along one side and q₂ = 8 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 8 µCq3 = 6 µCr13 = 6 cmr23 = 6 cm
F = N
6.Hard
3 cm3 cm+q1​ = +10 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 = 10 µC is 3 cm from it along one side and q₂ = 3 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 3 µCq3 = 4 µCr13 = 3 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 11.24 N
  2. 2. F = 89.9 N
  3. 3. E = 1.478 × 10⁷ N/C
  4. 4. F = 14.38 N
  5. 5. F = 123.6 N
  6. 6. F = 417.1 N

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