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In addition to the revision notes for Coulomb's Law on this page, you can also access the following Electrostatics learning resources for Coulomb's Law
Tutorial ID | Title | Tutorial | Video Tutorial | Revision Notes | Revision Questions | |
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14.2 | Coulomb's Law |
In these revision notes for Coulomb's Law, we cover the following key points:
During his famous experiment, Coulomb discovered that:
Putting all together, Coulomb obtained the following equation:
where k is a constant of proportionality.
The above equation is the mathematical expression of Coulomb's Law, which states that:
The electrical force between two charged objects is directly proportional to the product of the quantity of charge on the objects and inversely proportional to the square of the separation distance between the two objects.
Accurate measurements have shown that the value of constant k is
For simplicity, in most exercises we take k ≈ 9 × 109 N × m2 / C2.
The resultant force acting on a trial charge is zero when
where F1-0 and F2-0 are the forces applied by the charges Q1 and Q2 on the trial charge Q0. Therefore, the condition to have equilibrium at a point between two like charges is
where d is the distance of the trial charge from Q1 and r - d its distance from Q2.
If three or more charges are collinear, the resultant force acting on one of them lies according one dimension only. We simply add or subtract the individual forces as needed.
When charges are not collinear, the corresponding forces are not collinear either. In this case, we must consider their components according the basic directions separately and then, calculate the resultant force by using the Pythagorean Theorem.
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