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
++1 µC++5 µCr = 4 cm

Two point charges of +1 µC and +5 µC are 4 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = +5 µCr = 4 cm
F = N
2.Easy
++1 µC−−2 µCr = ?

Point charges of +1 µC and −2 µC exert a force of 5 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +1 µCq2 = −2 µCF = 5 N
r = cm
3.Medium
++1 µC−−6 µCP10 cm

A charge of +1 µC and a charge of −6 µC are 10 cm apart. Point P lies on the line between them, 5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = −6 µCr1 = 5 cmr2 = 5 cm
E = N/C
4.Medium
++1 µC++4 µCE = 040 cm

Charges of +1 µC and +4 µC are 40 cm apart. At what distance x from the +1 µC charge, on the line between them, is the electric field zero?

q1 = +1 µCq2 = +4 µCd = 40 cm
x = cm
5.Hard
10 cm8 cm+q1​ = +8 µC+q3​ = +8 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 8 µC is at the right-angle corner, q₁ = 8 µC is 10 cm from it along one side and q₂ = 5 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 5 µCq3 = 8 µCr13 = 10 cmr23 = 8 cm
F = N
6.Hard
8 cm8 cm+q1​ = +3 µC+q3​ = +4 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 3 µC is 8 cm from it along one side and q₂ = 5 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 3 µCq2 = 5 µCq3 = 4 µCr13 = 8 cmr23 = 8 cm
F = N

Answer key

  1. 1. F = 28.09 N
  2. 2. r = 5.997 cm
  3. 3. E = 2.517 × 10⁷ N/C
  4. 4. x = 13.33 cm
  5. 5. F = 80.42 N
  6. 6. F = 32.76 N

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