1. DAILY QUESTION March 31, 2009 1. What is the electric power equation?

2. Agenda3/31/09 Daily Question Daily Question Finish Sect 3 Notes Finish Sect 3 Notes Electric Power Practice Problems Electric Power Practice Problems Sect 3 Vocabulary Squares Sect 3 Vocabulary Squares Sect 3 Worksheet Sect 3 Worksheet Assignments: Assignments: 1. All Worksheets due 4/1

3. Electric Power Electric power is the rate at which electrical energy is used in a circuit Electric power is the rate at which electrical energy is used in a circuit Electric power is the product of total current (I) in and voltage (V) across a circuit Electric power is the product of total current (I) in and voltage (V) across a circuit Power (P) = current (I) x voltage (V) SI unit for power is: watt (W) SI unit for power is: watt (W)

4. The unit of energy that electric companies use to track consumption of energy is the kilowatt-hour. The unit of energy that electric companies use to track consumption of energy is the kilowatt-hour. Electric meters are used to determine how much electrical energy is consumed over a certain time interval Electric meters are used to determine how much electrical energy is consumed over a certain time interval

5. Overloaded Circuits When electrical wires carry more than a safe level of current When electrical wires carry more than a safe level of current May cause fires May cause fires Short circuits occur when two wires accidentally touch, creating an alternative pathway for current Short circuits occur when two wires accidentally touch, creating an alternative pathway for current

6. Fuses Prevent overloading of circuits Prevent overloading of circuits A fuse is a ribbon of wire with a low melting point A fuse is a ribbon of wire with a low melting point A “blown out” fuse is a sign that a short circuit or a circuit overload may exist A “blown out” fuse is a sign that a short circuit or a circuit overload may exist

7. Circuit Breakers Uses a magnet or bimetallic strip that responds to current overload by opening the circuit Uses a magnet or bimetallic strip that responds to current overload by opening the circuit Acts as a switch Acts as a switch Can be reset Can be reset