1.Easy
Two point charges of −5 µC and −6 µC are 3 cm apart. Find the magnitude of the electric force F between them. Use k = 8.99 × 10⁹ N·m²/C².
q1 = −5 µCq2 = −6 µCr = 3 cm
F = N
Coulomb’s law & electric fields worksheet with answers
2.Easy
Two point charges repel each other with a force of 40 N. The first charge is doubled and the distance between the charges is made four times as large. Find the new force F′.
F = 40 Nq₁′ = 2·q₁r′ = 4·r
F′ = N
3.Medium
Two identical small metal spheres carry charges of +10 µC and +3 µC. They are touched together and then put back 50 cm apart. Find the magnitude of the force F between them now. Use k = 8.99 × 10⁹ N·m²/C².
q1 = +10 µCq2 = +3 µCr = 50 cm
F = N
4.Medium
A charge of +10 µC and a charge of −2 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 = +10 µCq2 = −2 µCr1 = 15 cmr2 = 15 cm
E = N/C
5.Hard
Two identical small balls, each of mass 2 g, hang from the same point on insulating threads 80 cm long. They are given equal charges and each thread settles at 8° 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 = 2 gL = 80 cmθ = 8°g = 9.81 m/s²
q = nC
6.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 10 µC is at the right-angle corner, q₁ = 5 µC is 4 cm from it along one side and q₂ = 8 µC is 6 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 5 µCq2 = 8 µCq3 = 10 µCr13 = 4 cmr23 = 6 cm
F = N
Answer key
- 1. F = 299.7 N
- 2. F′ = 5 N
- 3. F = 1.519 N
- 4. E = 4.795 × 10⁶ N/C
- 5. q = 123.3 nC
- 6. F = 344.7 N
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