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
++4 µC++8 µCr = 12 cm

Two point charges of +4 µC and +8 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +4 µCq2 = +8 µCr = 12 cm
F = N
2.Easy
++100 nCPr = 5 cm

Find the magnitude of the electric field E at a distance of 5 cm from a point charge of +100 nC. Use k = 8.99 × 10⁹ N·m²/C².

q = +100 nCr = 5 cm
E = N/C
3.Medium
++1 µC++10 µCP10 cm

A charge of +1 µC and a charge of +10 µC are 10 cm apart. Point P lies on the line between them, 6 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = +10 µCr1 = 6 cmr2 = 4 cm
E = N/C
4.Medium
++6 µC++6 µCP60 cm

A charge of +6 µC and a charge of +6 µC are 60 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 = +6 µCq2 = +6 µCr1 = 15 cmr2 = 45 cm
E = N/C
5.Hard
5 cm5 cm+q1​ = +10 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 = 10 µC is 5 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 = 10 µCq2 = 5 µCq3 = 5 µCr13 = 5 cmr23 = 5 cm
F = N
6.Hard
3 cm3 cm+q1​ = +10 µC+q3​ = +3 µC+q2​ = +5 µC

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

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

Answer key

  1. 1. F = 19.98 N
  2. 2. E = 359600 N/C
  3. 3. E = 5.369 × 10⁷ N/C
  4. 4. E = 2.131 × 10⁶ N/C
  5. 5. F = 201 N
  6. 6. F = 335 N

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