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
−−10 µC++10 µCr = 20 cm

Two point charges of −10 µC and +10 µC are 20 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −10 µCq2 = +10 µCr = 20 cm
F = N
2.Easy
++8 µC−−10 µCr = 20 cm

Two point charges of +8 µC and −10 µC are 20 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +8 µCq2 = −10 µCr = 20 cm
F = N
3.Medium
−−8 µC++6 µCr = 10 cm

Two identical small metal spheres carry charges of −8 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 = −8 µCq2 = +6 µCr = 10 cm
F = N
4.Medium
++8 µC++2 µCE = 080 cm

Charges of +8 µC and +2 µC are 80 cm apart. At what distance x from the +8 µC charge, on the line between them, is the electric field zero?

q1 = +8 µCq2 = +2 µCd = 80 cm
x = cm
5.Hard
+−P2 × 8 cm10 cm+3 µC−3 µC

Charges of +3 µC and −3 µC are 16 cm apart. Point P lies 10 cm from the midpoint between them, on the perpendicular bisector. Find the magnitude of the electric field E at P. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +3 µCq2 = −3 µCd = 16 cmh = 10 cm
E = N/C
6.Hard
4 cm3 cm+q1​ = +3 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 = 3 µC is 4 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 = 3 µCq2 = 5 µCq3 = 5 µCr13 = 4 cmr23 = 3 cm
F = N

Answer key

  1. 1. F = 22.47 N
  2. 2. F = 17.98 N
  3. 3. F = 0.899 N
  4. 4. x = 53.33 cm
  5. 5. E = 2.055 × 10⁶ N/C
  6. 6. F = 263.6 N

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