Coulomb's Law Physics Example 3

Follow the full solution, then compare it with the other examples linked below.

Example 3

medium
If the distance between two charges is tripled, by what factor does the electrostatic force change?

Solution

  1. 1
    Coulomb's law: F∝1r2F \propto \frac{1}{r^2}.
  2. 2
    If r→3rr \to 3r: F′=F32=F9F' = \frac{F}{3^2} = \frac{F}{9}

Answer

The force decreases by a factor of 9\text{The force decreases by a factor of } 9
The inverse-square law means that tripling the distance reduces the force to one-ninth. This rapid decrease with distance is why electrostatic effects are mainly short-range in practice.

About Coulomb's Law

Coulomb's law gives the electric force between two point charges. The force gets larger when the charges are larger and gets smaller with the square.

Learn more about Coulomb's Law →

More Coulomb's Law Examples

Example 1 medium

Two charges [formula] and [formula] are separated by [formula]. What is the electrostatic force betw

Example 2 hard

Two identical charges experience a force of [formula] when separated by [formula]. What is the magni

Example 4 hard

Two charges [formula] and [formula] are separated by [formula]. (a) Calculate the force between them

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