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
++2 µC++1 µCr = 20 cm

Two point charges of +2 µC and +1 µC are 20 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = +1 µCr = 20 cm
F = N
2.Easy
++3 µC++6 µCr = ?

Point charges of +3 µC and +6 µC exert a force of 0.5 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +3 µCq2 = +6 µCF = 0.5 N
r = cm
3.Medium
++10 µC++2 µCP60 cm

A charge of +10 µC and a charge of +2 µC are 60 cm apart. Point P lies on the line between them, 30 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +10 µCq2 = +2 µCr1 = 30 cmr2 = 30 cm
E = N/C
4.Medium
−−1 µC−−5 µCr = 15 cm

Two identical small metal spheres carry charges of −1 µC and −5 µC. They are touched together and then put back 15 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².

q1 = −1 µCq2 = −5 µCr = 15 cm
F = N
5.Hard
8 cm8 cm+q1​ = +2 µC+q3​ = +5 µC+q2​ = +8 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 5 µC is at the right-angle corner, q₁ = 2 µC is 8 cm from it along one side and q₂ = 8 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 8 µCq3 = 5 µCr13 = 8 cmr23 = 8 cm
F = N
6.Hard
+−P2 × 6 cm5 cm+2 µC−2 µC

Charges of +2 µC and −2 µC are 12 cm apart. Point P lies 5 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 = +2 µCq2 = −2 µCd = 12 cmh = 5 cm
E = N/C

Answer key

  1. 1. F = 0.4495 N
  2. 2. r = 56.89 cm
  3. 3. E = 799111 N/C
  4. 4. F = 3.596 N
  5. 5. F = 57.92 N
  6. 6. E = 4.529 × 10⁶ N/C

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