Electric Force • Electric force - force exerted between two charged objects measured in Newtons • The closer the charges the greater the force between them.
Electric Force • Coulomb’s Law (1780’s) – electric force between 2 objects Felectric = Kc • q 1 • q 2 r 2 q 1 = charge #1 q 2 = charge #2 r = distance between charges Kc = Coulomb’s Constant in N • m 2/c 2 8. 99 x 109 N • m 2/c 2
Electric Force • Force is a vector quantity (magnitude and direction) • Force goes exactly between 2 objects in a straight line - +
Electric Force • Field force = no contact needed • Inversely proportional to the square of the distance of separation, bigger distance = less force.
Electric Force • Differences between electric and gravitational forces 1. Electric attracts / repels and Gravitational = always attracts 2. Electric is stronger than gravitational • Charge to overcome gravitational force is small
Electric Force • Principle of superposition → Resultant force on any one charge equals vector sum of the individual forces exerted on that charge by all of the other individual charges that are present.
Electric Force • Net external force = 0 N • In electrostatic situations the equilibrium position of a charge is the location in which the net electric force on the charge = 0 N