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
+q₁+q₂r

Two point charges repel each other with a force of 50 N. The first charge is doubled and the distance between the charges is tripled. Find the new force F′.

F = 50 Nq₁′ = 2·q₁r′ = 3·r
F′ = N
2.Easy
++10 µC++3 µCr = 10 cm

Two point charges of +10 µC and +3 µC are 10 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².

q1 = +10 µCq2 = +3 µCr = 10 cm
F = N
3.Medium
++5 µC−−8 µCP50 cm

A charge of +5 µC and a charge of −8 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 = +5 µCq2 = −8 µCr1 = 12.5 cmr2 = 37.5 cm
E = N/C
4.Medium
++1 µC++6 µCP40 cm

A charge of +1 µC and a charge of +6 µC are 40 cm apart. Point P lies on the line between them, 10 cm from the first charge. Find the magnitude of the electric field E at P.

q1 = +1 µCq2 = +6 µCr1 = 10 cmr2 = 30 cm
E = N/C
5.Hard
10 cm4 cm+q1​ = +10 µC+q3​ = +10 µC+q2​ = +4 µC

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

q1 = 10 µCq2 = 4 µCq3 = 10 µCr13 = 10 cmr23 = 4 cm
F = N
6.Hard
8 cm5 cm+q1​ = +1 µC+q3​ = +6 µC+q2​ = +8 µC

Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 1 µC is 8 cm from it along one side and q₂ = 8 µC is 5 cm from it along the other side. Find the magnitude of the net electric force F on q₃.

q1 = 1 µCq2 = 8 µCq3 = 6 µCr13 = 8 cmr23 = 5 cm
F = N

Answer key

  1. 1. F′ = 11.11 N
  2. 2. F = 26.97 N
  3. 3. E = 3.388 × 10⁶ N/C
  4. 4. E = 299667 N/C
  5. 5. F = 242.1 N
  6. 6. F = 172.8 N

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