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
−−6 µC−−5 µCr = 30 cm

Two point charges of −6 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 = −6 µCq2 = −5 µCr = 30 cm
F = N
2.Easy
++4 µC−−10 µCr = 20 cm

Two point charges of +4 µC and −10 µC are 20 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +4 µCq2 = −10 µCr = 20 cm
F = N
3.Medium
++4 µC−−6 µCP30 cm

A charge of +4 µC and a charge of −6 µC are 30 cm apart. Point P lies on the line between them, 7.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +4 µCq2 = −6 µCr1 = 7.5 cmr2 = 22.5 cm
E = N/C
4.Medium
++1 µC−−8 µCP60 cm

A charge of +1 µC and a charge of −8 µC are 60 cm apart. Point P lies on the line between them, 45 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = −8 µCr1 = 45 cmr2 = 15 cm
E = N/C
5.Hard
6 cm10 cm+q1​ = +3 µC+q3​ = +3 µC+q2​ = +3 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 3 µC is at the right-angle corner, q₁ = 3 µC is 6 cm from it along one side and q₂ = 3 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 3 µCq2 = 3 µCq3 = 3 µCr13 = 6 cmr23 = 10 cm
F = N
6.Hard
++P2 × 6 cm10 cm+4 µC+4 µC

Charges of +4 µC and +4 µC are 12 cm apart. Point P lies 10 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 = 12 cmh = 10 cm
E = N/C

Answer key

  1. 1. F = 2.997 N
  2. 2. F = 8.99 N
  3. 3. E = 7.458 × 10⁶ N/C
  4. 4. E = 3.241 × 10⁶ N/C
  5. 5. F = 23.89 N
  6. 6. E = 4.535 × 10⁶ N/C

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