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++2 µCr = 15 cm

Two point charges of +2 µC and +2 µC are 15 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = +2 µCr = 15 cm
F = N
2.Easy
++10 µC++3 µCr = 3 cm

Two point charges of +10 µC and +3 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +10 µCq2 = +3 µCr = 3 cm
F = N
3.Medium
++1 µC−−3 µCP10 cm

A charge of +1 µC and a charge of −3 µC are 10 cm apart. Point P lies on the line between them, 2.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = −3 µCr1 = 2.5 cmr2 = 7.5 cm
E = N/C
4.Medium
−−8 µC++4 µCr = 25 cm

Two identical small metal spheres carry charges of −8 µC and +4 µC. They are touched together and then put back 25 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −8 µCq2 = +4 µCr = 25 cm
F = N
5.Hard
10 cm5 cm+q1​ = +8 µC+q3​ = +1 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 8 µC is 10 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 = 8 µCq2 = 3 µCq3 = 1 µCr13 = 10 cmr23 = 5 cm
F = N
6.Hard
10 cm3 cm+q1​ = +2 µC+q3​ = +1 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 1 µC is at the right-angle corner, q₁ = 2 µC is 10 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 = 2 µCq2 = 5 µCq3 = 1 µCr13 = 10 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 1.598 N
  2. 2. F = 299.7 N
  3. 3. E = 1.918 × 10⁷ N/C
  4. 4. F = 0.5754 N
  5. 5. F = 12.97 N
  6. 6. F = 49.98 N

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