ELECTRIC CHARGES AND FORCES AP PHYSICS 1

ELECTRIC CHARGE Charges can be categorized into two arbitrary types: Positive Charges Negative Charges Objects with zero net charge are said to be eclectically neutral.

CHARGE OF AN ELECTRON

EXAMPLE # 1

CONSERVATION OF ELECTRIC CHARGE The total electric charge of the universe is constant. No physical process can result in an increase in the total amount of electric charge in the universe.

WAYS TO CHARGE AN OBJECT Charge separation – ex: friction, collisions Conduction – when a charged object comes into contact with another object Induction – when a charged object comes near a another object EXAMPLE # 2 Is the mass of an amber rod after charging with fur: a)Greater than b)Less than c)The same as Its mass before charging?

INSULATORS AND CONDUCTORS Insulators – charge does not move freely Examples: rubber, plastic, air Conductors – allow charges to move about more or less freely Examples: most metals, water Semiconductors – have both conductor and insulator properties. Example: silicon

COULOMB’S LAW EXAMPLE # 3 Find the electric force between two 1.00-C charges separated by 1.00m.

EXAMPLE #3 An electron and proton initially separated by a distance d, are released from rest simultaneously. The two particles are free to move. When they collide are they: a)At the midpoint of their initial separation b)Closer to the initial position of the proton c)Closer to the initial position of the electron

SUPERPOSITION OF FORCES Due to the fact that electric force, like all forces, is a vector quantity the net force is simply the vector sum of all of the forces taken individually.

EXAMPLE # 5