1.Easy
Two point charges repel each other with a force of 26 N. The first charge is tripled and the distance between the charges is doubled. Find the new force F′.
F = 26 Nq₁′ = 3·q₁r′ = 2·r
F′ = N
Coulomb’s law & electric fields worksheet with answers
2.Easy
Two point charges of +3 µC and +5 µC are 5 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².
q1 = +3 µCq2 = +5 µCr = 5 cm
F = N
3.Medium
A charge of +1 µC and a charge of −6 µC are 10 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 = +1 µCq2 = −6 µCr1 = 7.5 cmr2 = 2.5 cm
E = N/C
4.Medium
A charge of +3 µC and a charge of −4 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 = −4 µCr1 = 15 cmr2 = 15 cm
E = N/C
5.Hard
Two identical small balls, each of mass 5 g, hang from the same point on insulating threads 80 cm long. They are given equal charges and each thread settles at 10° 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 = 5 gL = 80 cmθ = 10°g = 9.81 m/s²
q = nC
6.Hard
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 6 cm from it along one side and q₂ = 3 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 2 µCq2 = 3 µCq3 = 5 µCr13 = 6 cmr23 = 6 cm
F = N
Answer key
- 1. F′ = 19.5 N
- 2. F = 53.94 N
- 3. E = 8.79 × 10⁷ N/C
- 4. E = 2.797 × 10⁶ N/C
- 5. q = 272.5 nC
- 6. F = 45.02 N
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