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
−−5 µC++10 µCr = 12 cm

Two point charges of −5 µC and +10 µC are 12 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 = 12 cm
F = N
2.Easy
−−3 µC++8 µCr = 6 cm

Two point charges of −3 µC and +8 µC are 6 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −3 µCq2 = +8 µCr = 6 cm
F = N
3.Medium
++2 µC−−3 µCr = 15 cm

Two identical small metal spheres carry charges of +2 µC and −3 µC. They are touched together and then put back 15 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = −3 µCr = 15 cm
F = N
4.Medium
++5 µC++4 µC++10 µC12 cm + 8 cm

Three point charges lie on a straight line: +5 µC on the left, +10 µC on the right 20 cm away, and +4 µC between them, 12 cm from the left charge. Find the magnitude of the net electric force F on the middle charge. Use k = 8.99 × 10⁹ N·m²/C².

qL = +5 µCqR = +10 µCqM = +4 µCrL = 12 cmrR = 8 cm
F = N
5.Hard
8 cm10 cm+q1​ = +8 µC+q3​ = +1 µC+q2​ = +10 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 8 cm from it along one side and q₂ = 10 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 10 µCq3 = 1 µCr13 = 8 cmr23 = 10 cm
F = N
6.Hard
4 cm5 cm+q1​ = +3 µC+q3​ = +5 µC+q2​ = +10 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 5 µC is at the right-angle corner, q₁ = 3 µC is 4 cm from it along one side and q₂ = 10 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 3 µCq2 = 10 µCq3 = 5 µCr13 = 4 cmr23 = 5 cm
F = N

Answer key

  1. 1. F = 31.22 N
  2. 2. F = 59.93 N
  3. 3. F = 0.09989 N
  4. 4. F = 43.7 N
  5. 5. F = 14.39 N
  6. 6. F = 198.6 N

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