1.Easy
Two point charges repel each other with a force of 24 N. The first charge is halved and the distance between the charges is doubled. Find the new force F′.
F = 24 Nq₁′ = 0.5·q₁r′ = 2·r
F′ = N
Coulomb’s law & electric fields worksheet with answers
2.Easy
Two point charges of +8 µC and +8 µC are 2 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².
q1 = +8 µCq2 = +8 µCr = 2 cm
F = N
3.Medium
Charges of +2 µC and +6 µC are 20 cm apart. At what distance x from the +2 µC charge, on the line between them, is the electric field zero?
q1 = +2 µCq2 = +6 µCd = 20 cm
x = cm
4.Medium
Three point charges lie on a straight line: +5 µC on the left, −3 µC on the right 10 cm away, and +2 µC between them, 5 cm from the left charge. Find the magnitude of the net electric force F on the middle charge. Use k = 8.99 × 10⁹ N·m²/C².
qL = +5 µCqR = −3 µCqM = +2 µCrL = 5 cmrR = 5 cm
F = N
5.Hard
Two identical small balls, each of mass 1 g, hang from the same point on insulating threads 100 cm long. They are given equal charges and each thread settles at 5° from the vertical. Use g = 9.81 m/s². Find the charge q on each ball in nC. Use k = 8.99 × 10⁹ N·m²/C².
m = 1 gL = 100 cmθ = 5°g = 9.81 m/s²
q = nC
6.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 2 µC is at the right-angle corner, q₁ = 8 µC is 6 cm from it along one side and q₂ = 6 µC is 3 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 8 µCq2 = 6 µCq3 = 2 µCr13 = 6 cmr23 = 3 cm
F = N
Answer key
- 1. F′ = 3 N
- 2. F = 1438 N
- 3. x = 7.321 cm
- 4. F = 57.54 N
- 5. q = 53.86 nC
- 6. F = 126.4 N
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