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
++3 µCPr = 8 cm

Find the magnitude of the electric field E at a distance of 8 cm from a point charge of +3 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = +3 µCr = 8 cm
E = N/C
2.Easy
−−1 µC−−6 µCr = 4 cm

Two point charges of −1 µC and −6 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 = −6 µCr = 4 cm
F = N
3.Medium
++10 µC++3 µCr = 15 cm

Two identical small metal spheres carry charges of +10 µC and +3 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 = +10 µCq2 = +3 µCr = 15 cm
F = N
4.Medium
++2 µC++8 µCP50 cm

A charge of +2 µC and a charge of +8 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 = +2 µCq2 = +8 µCr1 = 20 cmr2 = 30 cm
E = N/C
5.Hard
8 cm5 cm+q1​ = +3 µC+q3​ = +10 µC+q2​ = +5 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 10 µC is at the right-angle corner, q₁ = 3 µC is 8 cm from it along one side and q₂ = 5 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 3 µCq2 = 5 µCq3 = 10 µCr13 = 8 cmr23 = 5 cm
F = N
6.Hard
++P2 × 8 cm3 cm+4 µC+4 µC

Charges of +4 µC and +4 µC are 16 cm apart. Point P lies 3 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 = +4 µCq2 = +4 µCd = 16 cmh = 3 cm
E = N/C

Answer key

  1. 1. E = 4.214 × 10⁶ N/C
  2. 2. F = 33.71 N
  3. 3. F = 16.88 N
  4. 4. E = 349611 N/C
  5. 5. F = 184.7 N
  6. 6. E = 3.459 × 10⁶ N/C

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