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
++6 µC++3 µCr = 12 cm

Two point charges of +6 µC and +3 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +6 µCq2 = +3 µCr = 12 cm
F = N
2.Easy
−−5 µC++10 µCr = 8 cm

Two point charges of −5 µC and +10 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 = +10 µCr = 8 cm
F = N
3.Medium
++5 µC++3 µCr = 30 cm

Two identical small metal spheres carry charges of +5 µC and +3 µC. They are touched together and then put back 30 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +5 µCq2 = +3 µCr = 30 cm
F = N
4.Medium
−−1 µC++2 µCr = 5 cm

Two identical small metal spheres carry charges of −1 µC and +2 µC. They are touched together and then put back 5 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −1 µCq2 = +2 µCr = 5 cm
F = N
5.Hard
3 cm10 cm+q1​ = +10 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 = 10 µC is 3 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 = 10 µCq2 = 4 µCq3 = 10 µCr13 = 3 cmr23 = 10 cm
F = N
6.Hard
6 cm3 cm+q1​ = +6 µC+q3​ = +5 µC+q2​ = +4 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 5 µC is at the right-angle corner, q₁ = 6 µC is 6 cm from it along one side and q₂ = 4 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 6 µCq2 = 4 µCq3 = 5 µCr13 = 6 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 11.24 N
  2. 2. F = 70.23 N
  3. 3. F = 1.598 N
  4. 4. F = 0.899 N
  5. 5. F = 999.5 N
  6. 6. F = 213.4 N

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