Transcript Electricity
Electricity Electric Charge Charged part of atom: proton & electron Proton = + Electron = Like charges repel; opposite charges attract Electric Fields Electric charge exerts a force through the electric field that surrounds the charge Electric field extends outward from every charged particle Static Charge Objects become charged by gaining or losing electrons. Gain electrons = negative charge Lose electrons = positive charge The buildup of charges on an object is called static electricity. Static Electricity Behaves differently than electric currents In electric currents, charges move continuously. In static electricity, charges build up, but DO NOT FLOW. Static Electricity 3 methods by which charges are transferred Friction One object rubbing against another Conduction Direct contact Induction Movement of electrons to one part of an object caused by the electric field of another Static Discharge Negatively charged object & positively charged object are brought together….electrons move until both objects have the same charge. The loss of static electricity is called static discharge. Static Discharge Lightening Can occur within a cloud, between 2 clouds, or between cloud and earth Static Discharge Electroscope: used to detect static discharge A static charge is different from current electricity in that a static charge A. never moves. B. can either move or not move. C. moves only when resistance is low enough. D. moves only when voltage is high enough. Electric Current The flow of electric charges Measured in amperes (A) or amps Always flow from a region of higher potential energy to region of lower potential energy Difference in potential energy between 2 locations is called potential difference Potential Difference Also called voltage Measured in volts (V) Provides the force that pushes the charge through a circuit Battery (6 volts) Potential energy difference is created by the positive and negative terminals on the battery Potential Difference Electrons will flow as long as there is a potential difference, or voltage between 2 parts of a circuit. Voltage causes current to flow! Voltage Increase voltage….increase flow of electric current resistance Current depends on resistance offered by the material through which it travels The greater the resistance…the less current there is for a given voltage Current takes the path of least resistance! Why aren’t the birds on the wire hurt by the electric current that is flowing through the wire? Ohm’s Law Resistance = voltage/current Ohms = volts/amps Circuits A path through which electricity can flow. Only flow when there is potential difference (voltage) Circuits Most have 3 parts Energy source Needs this to push a charge thru a circuit; battery One or more loads Light bulbs, bells, radios, motors Conductor Material that allows electrical energy to easily flow thru it; metals Circuits resistor An object added to a circuit that restricts the flow of electrical energy. Produce a voltage drop Used to produce the desired potential difference (voltage) Limit current; cause some electrical energy to be given off as heat Circuits Switch Device used to control the flow of current thru a circuit Separates (open) or brings together (closed) 2 conductors attached to a switch Open…NO electricity can flow Closed…electricity flows Series Circuits Provides only ONE path for the flow of current Loads are set up in a series, or line. A failure or break in any part of the circuit results in the stopping of the flow of electricity thru the entire circuit. All loads share the same energy source. Current added. lowers as more loads are Series circuit Parallel Circuits Offers more than one path for the flow of electricity Each load has its own circuit pathway to the energy source…each has its own path for electricity If one part fails, it does not affect the rest of the circuit Loads do NOT share current; have full voltage of energy source Adding more loads does not affect the current flowing to other loads…lights will not dim