1.Easy
Point charges of +1 µC and −1 µC exert a force of 10 N on each other. How far apart r are they? Give the answer in cm. Use k = 8.99 × 10⁹ N·m²/C².
q1 = +1 µCq2 = −1 µCF = 10 N
r = cm
Coulomb’s law & electric fields worksheet with answers
2.Easy
Find the magnitude of the electric field E at a distance of 2 cm from a point charge of −2 µC. Use k = 8.99 × 10⁹ N·m²/C².
q = −2 µCr = 2 cm
E = N/C
3.Medium
A charge of +6 µC and a charge of +3 µC are 50 cm apart. Point P lies on the line between them, 20 cm from the first charge. Find the magnitude of the electric field E at P.
q1 = +6 µCq2 = +3 µCr1 = 20 cmr2 = 30 cm
E = N/C
4.Medium
A charge of +1 µC and a charge of −6 µC are 40 cm apart. Point P lies on the line between them, 30 cm from the first charge. Find the magnitude of the electric field E at P.
q1 = +1 µCq2 = −6 µCr1 = 30 cmr2 = 10 cm
E = N/C
5.Hard
Two identical small balls, each of mass 3 g, hang from the same point on insulating threads 80 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 = 80 cmθ = 20°g = 9.81 m/s²
q = nC
6.Hard
Three positive point charges sit at the corners of a right triangle: q₃ = 4 µC is at the right-angle corner, q₁ = 3 µC is 3 cm from it along one side and q₂ = 10 µC is 8 cm from it along the other side. Find the magnitude of the net electric force F on q₃.
q1 = 3 µCq2 = 10 µCq3 = 4 µCr13 = 3 cmr23 = 8 cm
F = N
Answer key
- 1. r = 2.998 cm
- 2. E = 4.495 × 10⁷ N/C
- 3. E = 1.049 × 10⁶ N/C
- 4. E = 5.494 × 10⁶ N/C
- 5. q = 597.3 nC
- 6. F = 132.4 N
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