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
−−3 µC++6 µCr = 25 cm

Two point charges of −3 µC and +6 µC are 25 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −3 µCq2 = +6 µCr = 25 cm
F = N
2.Easy
++3 µC−−10 µCr = 4 cm

Two point charges of +3 µC and −10 µC are 4 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +3 µCq2 = −10 µCr = 4 cm
F = N
3.Medium
−−6 µC++3 µC++4 µC5 cm + 15 cm

Three point charges lie on a straight line: −6 µC on the left, +4 µC on the right 20 cm away, and +3 µC between them, 5 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 = −6 µCqR = +4 µCqM = +3 µCrL = 5 cmrR = 15 cm
F = N
4.Medium
++1 µC−−6 µCr = 10 cm

Two identical small metal spheres carry charges of +1 µC and −6 µC. They are touched together and then put back 10 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = −6 µCr = 10 cm
F = N
5.Hard
8 cm3 cm+q1​ = +10 µC+q3​ = +2 µC+q2​ = +1 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 10 µC is 8 cm from it along one side and q₂ = 1 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 10 µCq2 = 1 µCq3 = 2 µCr13 = 8 cmr23 = 3 cm
F = N
6.Hard
5 cm4 cm+q1​ = +3 µC+q3​ = +10 µC+q2​ = +10 µC

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

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

Answer key

  1. 1. F = 2.589 N
  2. 2. F = 168.6 N
  3. 3. F = 69.52 N
  4. 4. F = 5.619 N
  5. 5. F = 34.47 N
  6. 6. F = 572.1 N

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