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
++4 µC−−10 µCr = 4 cm

Two point charges of +4 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 = +4 µCq2 = −10 µCr = 4 cm
F = N
2.Easy
−−3 µC−−5 µCr = 10 cm

Two point charges of −3 µC and −5 µC are 10 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −3 µCq2 = −5 µCr = 10 cm
F = N
3.Medium
++3 µC−−1 µCP50 cm

A charge of +3 µC and a charge of −1 µC are 50 cm apart. Point P lies on the line between them, 25 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +3 µCq2 = −1 µCr1 = 25 cmr2 = 25 cm
E = N/C
4.Medium
++6 µC++8 µC−−5 µC7.5 cm + 2.5 cm

Three point charges lie on a straight line: +6 µC on the left, −5 µC on the right 10 cm away, and +8 µC between them, 7.5 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 = −5 µCqM = +8 µCrL = 7.5 cmrR = 2.5 cm
F = N
5.Hard
++P2 × 8 cm4 cm+6 µC+6 µC

Charges of +6 µC and +6 µC are 16 cm apart. Point P lies 4 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 = +6 µCq2 = +6 µCd = 16 cmh = 4 cm
E = N/C
6.Hard
4 cm6 cm+q1​ = +8 µC+q3​ = +1 µC+q2​ = +1 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 4 cm from it along one side and q₂ = 1 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 1 µCq3 = 1 µCr13 = 4 cmr23 = 6 cm
F = N

Answer key

  1. 1. F = 224.7 N
  2. 2. F = 13.48 N
  3. 3. E = 575360 N/C
  4. 4. F = 652.1 N
  5. 5. E = 6.031 × 10⁶ N/C
  6. 6. F = 45.02 N

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