Electric Forces - Coulomb's Law

Question 1

coulombs law

Answer 1

• When two (or more) electric charges are close to each other, they exert an electrical force “Fe” on each other.
• As always, the forces they exert on each other are equal and opposite. The amount of the force depends on how much charge there is (more charge means more force) and how far apart the charges are (greater distance means less force). The equation for calculating the amount of electric force between two charges is called “Coulomb’s Law”:
• The number ke is a constant; it is always the same.
  Coulomb’s Law only tells you the magnitude of the electric force; that’s why there is an absolute value sign on it. The direction of the electrical force is either toward the other charge (if they are opposites) or away from the other charge (if they are similar).
  Note that the electric force dies off as the square of the distance. For example, if you double the distance between two charges, the force is not cut in half; it is cut in (1/2)2 = 1/4.
• Like any other force, electric forces cause masses to accelerate. If you find Fe, you can set it equal to ma to find the acceleration.
• Because a Coulomb is a such a large unit of charge, most problems will have micro-Coulombs (10-6) or nano-Coulombs (10-9). Watch out for that, and be sure to enter the correct power in the calculator.