DAILY QUESTION

March 31, 2009

1. What is the electric power equation?

AgendaAgenda 3/31/093/31/09

Daily QuestionDaily Question Finish Sect 3 NotesFinish Sect 3 Notes Electric Power Practice ProblemsElectric Power Practice Problems Sect 3 Vocabulary SquaresSect 3 Vocabulary Squares Sect 3 WorksheetSect 3 Worksheet Assignments: Assignments:

1. All Worksheets due 4/11. All Worksheets due 4/1

Electric PowerElectric Power

Electric power is the rate at which Electric power is the rate at which electrical energy is used in a circuitelectrical energy is used in a circuit

Electric power is the product of total Electric power is the product of total current (I) in and voltage (V) across a current (I) in and voltage (V) across a circuitcircuit

Power (P) = current (I) x Power (P) = current (I) x voltage (V)voltage (V)

SI unit for power is: watt (W)SI unit for power is: watt (W)

The unit of energy that electric The unit of energy that electric companies use to track consumption companies use to track consumption of energy is the kilowatt-hour.of energy is the kilowatt-hour.

Electric meters are used to Electric meters are used to determine how much electrical determine how much electrical energy is consumed over a certain energy is consumed over a certain time intervaltime interval

Overloaded CircuitsOverloaded Circuits

When electrical wires carry more When electrical wires carry more than a safe level of currentthan a safe level of current

May cause firesMay cause fires Short circuits occur when two wires Short circuits occur when two wires

accidentally touch, creating an accidentally touch, creating an alternative pathway for currentalternative pathway for current

FusesFuses

Prevent overloading of circuitsPrevent overloading of circuits A fuse is a ribbon of wire with a low A fuse is a ribbon of wire with a low

melting pointmelting point A “blown out” fuse is a sign that a A “blown out” fuse is a sign that a

short circuit or a circuit overload may short circuit or a circuit overload may existexist

Circuit BreakersCircuit Breakers

Uses a magnet or bimetallic strip Uses a magnet or bimetallic strip that responds to current overload by that responds to current overload by opening the circuitopening the circuit

Acts as a switchActs as a switch Can be reset Can be reset