1.Easy
Two point charges of −3 µC and +4 µC are 12 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².
q1 = −3 µCq2 = +4 µCr = 12 cm
F = N
Coulomb’s law & electric fields worksheet with answers
2.Easy
Two point charges repel each other with a force of 42 N. The first charge is halved and the distance between the charges is doubled. Find the new force F′.
F = 42 Nq₁′ = 0.5·q₁r′ = 2·r
F′ = N
3.Medium
A charge of +1 µC and a charge of −3 µC are 10 cm apart. Point P lies on the line between them, 2.5 cm from the first charge. Find the magnitude of the electric field E at P.
q1 = +1 µCq2 = −3 µCr1 = 2.5 cmr2 = 7.5 cm
E = N/C
4.Medium
A charge of +4 µC and a charge of +8 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 = +4 µCq2 = +8 µCr1 = 10 cmr2 = 30 cm
E = N/C
5.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 5 µC is at the right-angle corner, q₁ = 10 µC is 3 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 = 10 µCq2 = 6 µCq3 = 5 µCr13 = 3 cmr23 = 6 cm
F = N
6.Hard
Two identical small balls, each of mass 3 g, hang from the same point on insulating threads 40 cm long. They are given equal charges and each thread settles at 20° 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 = 3 gL = 40 cmθ = 20°g = 9.81 m/s²
q = nC
Answer key
- 1. F = 7.492 N
- 2. F′ = 5.25 N
- 3. E = 1.918 × 10⁷ N/C
- 4. E = 2.797 × 10⁶ N/C
- 5. F = 505 N
- 6. q = 298.7 nC
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