1.Easy
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
Coulomb’s law & electric fields worksheet with answers
2.Easy
Two point charges of +8 µC and −4 µC are 20 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².
q1 = +8 µCq2 = −4 µCr = 20 cm
F = N
3.Medium
A charge of +5 µC and a charge of +4 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 = +5 µCq2 = +4 µCr1 = 2.5 cmr2 = 7.5 cm
E = N/C
4.Medium
A charge of +4 µC and a charge of −1 µC are 50 cm apart. Point P lies on the line between them, 37.5 cm from the first charge. Find the magnitude of the electric field E at P.
q1 = +4 µCq2 = −1 µCr1 = 37.5 cmr2 = 12.5 cm
E = N/C
5.Hard
Two identical small balls, each of mass 1 g, hang from the same point on insulating threads 20 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 = 1 gL = 20 cmθ = 20°g = 9.81 m/s²
q = nC
6.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 3 µC is 6 cm from it along one side and q₂ = 3 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 3 µCq2 = 3 µCq3 = 6 µCr13 = 6 cmr23 = 8 cm
F = N
Answer key
- 1. F′ = 11.11 N
- 2. F = 7.192 N
- 3. E = 6.553 × 10⁷ N/C
- 4. E = 831076 N/C
- 5. q = 86.22 nC
- 6. F = 51.57 N
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