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
++200 nCPr = 25 cm

Find the magnitude of the electric field E at a distance of 25 cm from a point charge of +200 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = +200 nCr = 25 cm
E = N/C
2.Easy
++5 µC−−2 µCr = 8 cm

Two point charges of +5 µC and −2 µC are 8 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +5 µCq2 = −2 µCr = 8 cm
F = N
3.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, 30 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = −2 µCr1 = 30 cmr2 = 20 cm
E = N/C
4.Medium
++1 µC−−8 µCP40 cm

A charge of +1 µC and a charge of −8 µC are 40 cm apart. Point P lies on the line between them, 16 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = −8 µCr1 = 16 cmr2 = 24 cm
E = N/C
5.Hard
4 cm5 cm+q1​ = +2 µC+q3​ = +5 µC+q2​ = +5 µC

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

q1 = 2 µCq2 = 5 µCq3 = 5 µCr13 = 4 cmr23 = 5 cm
F = N
6.Hard
5 cm10 cm+q1​ = +6 µC+q3​ = +10 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 10 µC is at the right-angle corner, q₁ = 6 µC is 5 cm from it along one side and q₂ = 4 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 4 µCq3 = 10 µCr13 = 5 cmr23 = 10 cm
F = N

Answer key

  1. 1. E = 28768 N/C
  2. 2. F = 14.05 N
  3. 3. E = 948944 N/C
  4. 4. E = 1.6 × 10⁶ N/C
  5. 5. F = 106 N
  6. 6. F = 218.7 N

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