1.Easy
Two point charges repel each other with a force of 50 N. The first charge is halved and the distance between the charges is doubled. Find the new force F′.
F = 50 Nq₁′ = 0.5·q₁r′ = 2·r
F′ = N
Coulomb’s law & electric fields worksheet with answers
2.Easy
Two point charges of −4 µC and +10 µC are 15 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².
q1 = −4 µCq2 = +10 µCr = 15 cm
F = N
3.Medium
A charge of +6 µC and a charge of +6 µC are 20 cm apart. Point P lies on the line between them, 8 cm from the first charge. Find the magnitude of the electric field E at P.
q1 = +6 µCq2 = +6 µCr1 = 8 cmr2 = 12 cm
E = N/C
4.Medium
A charge of +1 µC and a charge of +4 µC are 20 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 = +1 µCq2 = +4 µCr1 = 15 cmr2 = 5 cm
E = N/C
5.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 6 µC is at the right-angle corner, q₁ = 5 µC is 8 cm from it along one side and q₂ = 2 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 5 µCq2 = 2 µCq3 = 6 µCr13 = 8 cmr23 = 8 cm
F = N
6.Hard
Two identical small balls, each of mass 5 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 = 5 gL = 20 cmθ = 20°g = 9.81 m/s²
q = nC
Answer key
- 1. F′ = 6.25 N
- 2. F = 15.98 N
- 3. E = 4.682 × 10⁶ N/C
- 4. E = 1.398 × 10⁷ N/C
- 5. F = 45.39 N
- 6. q = 192.8 nC
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