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
++10 µCPr = 2 cm

Find the magnitude of the electric field E at a distance of 2 cm from a point charge of +10 µC. Use k = 8.99 × 10⁹ N·m²/C².

q = +10 µCr = 2 cm
E = N/C
2.Easy
++8 µC−−6 µCr = ?

Point charges of +8 µC and −6 µC exert a force of 10 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +8 µCq2 = −6 µCF = 10 N
r = cm
3.Medium
++6 µC−−5 µCP50 cm

A charge of +6 µC and a charge of −5 µC are 50 cm apart. Point P lies on the line between them, 12.5 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +6 µCq2 = −5 µCr1 = 12.5 cmr2 = 37.5 cm
E = N/C
4.Medium
++3 µC−−10 µCP30 cm

A charge of +3 µC and a charge of −10 µC are 30 cm apart. Point P lies on the line between them, 15 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +3 µCq2 = −10 µCr1 = 15 cmr2 = 15 cm
E = N/C
5.Hard
6 cm10 cm+q1​ = +8 µC+q3​ = +4 µC+q2​ = +6 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 8 µC is 6 cm from it along one side and q₂ = 6 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 8 µCq2 = 6 µCq3 = 4 µCr13 = 6 cmr23 = 10 cm
F = N
6.Hard
5 cm10 cm+q1​ = +2 µC+q3​ = +5 µC+q2​ = +2 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 5 cm from it along one side and q₂ = 2 µC is 10 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 2 µCq2 = 2 µCq3 = 5 µCr13 = 5 cmr23 = 10 cm
F = N

Answer key

  1. 1. E = 2.247 × 10⁸ N/C
  2. 2. r = 20.77 cm
  3. 3. E = 3.772 × 10⁶ N/C
  4. 4. E = 5.194 × 10⁶ N/C
  5. 5. F = 82.77 N
  6. 6. F = 37.07 N

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