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−−8 µCr = 4 cm

Two point charges of +2 µC and −8 µC are 4 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +2 µCq2 = −8 µCr = 4 cm
F = N
2.Easy
−−5 µCPr = 8 cm

Find the magnitude of the electric field E at a distance of 8 cm from a point charge of −5 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = −5 µCr = 8 cm
E = N/C
3.Medium
++2 µC++1 µCP60 cm

A charge of +2 µC and a charge of +1 µC are 60 cm apart. Point P lies on the line between them, 36 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +2 µCq2 = +1 µCr1 = 36 cmr2 = 24 cm
E = N/C
4.Medium
++1 µC−−10 µCr = 15 cm

Two identical small metal spheres carry charges of +1 µC and −10 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 = −10 µCr = 15 cm
F = N
5.Hard
5 cm6 cm+q1​ = +4 µC+q3​ = +8 µC+q2​ = +6 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 8 µC is at the right-angle corner, q₁ = 4 µC is 5 cm from it along one side and q₂ = 6 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 4 µCq2 = 6 µCq3 = 8 µCr13 = 5 cmr23 = 6 cm
F = N
6.Hard
++P2 × 3 cm4 cm+4 µC+4 µC

Charges of +4 µC and +4 µC are 6 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 = +4 µCq2 = +4 µCd = 6 cmh = 4 cm
E = N/C

Answer key

  1. 1. F = 89.9 N
  2. 2. E = 7.023 × 10⁶ N/C
  3. 3. E = 17342 N/C
  4. 4. F = 8.091 N
  5. 5. F = 166.2 N
  6. 6. E = 2.301 × 10⁷ N/C

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