Electric Charge

MATTER

AMBER a hard translucent fossil resin varying in color from yellow to light :Amber.pendants.800pix jpg supplies.com/Prod4/amber_insect1.jpg

BENJAMIN FRANKLIN INTRODUCED THE IDEA THAT ALL SUBSTANCES ARE PENETRATED BY AN ELECTRIC FIRE TOO MUCH ELECTRIC FIRE= POSITIVE CHARGE LACK OF ELECTRIC FIRE= NEGATIVE CHARGE

Electrostatics The study of the interactions between electric charges that are at rest (or nearly so).

ELECTRIC CHARGE Fundamental quantity in electrostatics Two kinds of charge: positive and negative

Elementary Charge

Electric Attraction and Repulsion LIKE CHARGES REPEL: Two positive charges repel each other Two negative charges repel each other UNLIKE CHARGES ATTRACT: Negative charge attracts positive charge.

Law of Conservation of Charge THE NET AMOUNT OF CHARGE PRODUCED IN ANY PROCESS IS ZERO; NO NET ELECTRIC CHARGE CAN BE CREATED OR DESTROYED

Conductors, Insulators, and Ground Conductor- material that permit the flow of electric charge Insulator- material that do not allow the flow of electric charge readily Ground- a neutral material that can accept or supply an essentially unlimited number of charges

PLEASE SEE VIDEO DEMONSTRATION

CHARGING PROCESS CONDUCTION- charging neutral object by placing charge object in contact with the neutral object INDUCTION- charging neutral object by placing charge object near the neutral object without physical contact

INDUCTION PROCESS

ELECTROSCOPE A device that can be used for detecting charge a,a- - thin leaves of metal foil b - metal support c - glass container d - metal knob

COULOMB’S LAW  Applicable to point charges (objects whose size is much smaller than the distance between them)  Describes the interaction of electric charges

EX 1. ELECTRIC FORCE ON ELECTRON BY PROTON Determine the magnitude and direction of the electric force on the electron of a hydrogen atom exerted by the single proton that is the atom’s nucleus. Assume the average distance between the revolving electron and the proton is r= 0.53 x m.

 Two point charges, q1= +25nC and q2= - 75nC, are separated by a distance of 3.0 cm. Find the magnitude and direction of a) The electric force that q1 exerts on q2; and b) The electric force that q2 exerts on q1.

PRINCIPLE OF SUPERPOSITION OF FORCES States that when two or more forces exerted by two or more charges on a charge, the total force on that charge is the vector sum of the forces exerted by the individual charges.

Two point charges are located on the positive x- axis of a coordinate system. Charge q1 = 1.0 nC is 2.0 cm from the origin, and charge q2 = nC is 4.0 cm from the origin. What is the total force exerted by these two charges on a charge q3 = 5.0 nC located at the origin? Gravitational forces are negligible.