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++5 µCr = 30 cm

Two point charges of +5 µC and +5 µC are 30 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +5 µCq2 = +5 µCr = 30 cm
F = N
2.Easy
++5 µC++6 µCr = ?

Point charges of +5 µC and +6 µC exert a force of 2 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +5 µCq2 = +6 µCF = 2 N
r = cm
3.Medium
++5 µC++4 µCE = 010 cm

Charges of +5 µC and +4 µC are 10 cm apart. At what distance x from the +5 µC charge, on the line between them, is the electric field zero?

q1 = +5 µCq2 = +4 µCd = 10 cm
x = cm
4.Medium
++5 µC++10 µCP50 cm

A charge of +5 µC and a charge of +10 µC are 50 cm apart. Point P lies on the line between them, 20 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +5 µCq2 = +10 µCr1 = 20 cmr2 = 30 cm
E = N/C
5.Hard
3 cm3 cm+q1​ = +2 µC+q3​ = +8 µC+q2​ = +8 µC

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

q1 = 2 µCq2 = 8 µCq3 = 8 µCr13 = 3 cmr23 = 3 cm
F = N
6.Hard
4 cm5 cm+q1​ = +6 µC+q3​ = +5 µC+q2​ = +3 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 4 cm from it along one side and q₂ = 3 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

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

Answer key

  1. 1. F = 2.497 N
  2. 2. r = 36.72 cm
  3. 3. x = 5.279 cm
  4. 4. E = 124861 N/C
  5. 5. F = 659 N
  6. 6. F = 177 N

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