What is a circuit? A set of connected electrical components that provide one or more complete paths for the movement of charges. A set of connected electrical components that provide one or more complete paths for the movement of charges. A complete path from one battery terminal to another = “closed circuit” A complete path from one battery terminal to another = “closed circuit” Any break in the path = “open circuit” Any break in the path = “open circuit”

Circuit diagrams Circuit/schematic diagrams are used to represent electric circuits. Circuit/schematic diagrams are used to represent electric circuits. Symbols include: Symbols include: Wire Battery Resistor Light Bulb Switch +-

Simple Circuit Diagram Simple circuit = power source, wire, and bulb

Types of Circuits Two types: Two types: 1. Series circuit - provides a single conducting path without junctions. - the current has only one loop to flow through - the current has only one loop to flow through - the amount of current is the same through every part - the amount of current is the same through every part

Series Circuits - Output devices that are connected in the same loop are in “series” - What happens when there is a break in the connection? BOTH LIGHTS GO OUT!!!

Calculating Current Voltage is calculated as the sum of voltage drops across the circuit. Voltage is calculated as the sum of voltage drops across the circuit. V source =V A + V B V source =V A + V B Equivalent resistances R=R A + R B + … Equivalent resistances R=R A + R B + … Current I=V/R Current I=V/R Remember 1 Ampere is = 1 C/s. There are 6.24x10 18 electrons in a Coulomb Remember 1 Ampere is = 1 C/s. There are 6.24x10 18 electrons in a Coulomb

2. Parallel Circuit - contains two or more branches for current to move through. - Individual parts can be turned off without affecting the entire circuit. Ex: electrical system in a house - Electrical energy enters your home at the circuit breaker or fuse box. - Electrical energy enters your home at the circuit breaker or fuse box. - Guards against overheating electric wires. - Guards against overheating electric wires. Types of Circuits

Parallel Circuit A B What happens when switch A breaks the connection? Switch B?

Calculating Resistance and Current in a Parallel Circuit R=V/I R=V/I Equivalent Resistance 1/R=1/R A + 1/R B +… Equivalent Resistance 1/R=1/R A + 1/R B +…

Circuit Question Why are some Christmas tree lights more expensive than others that do the same job? What are the advantages of the more expensive lights? Why are some Christmas tree lights more expensive than others that do the same job? What are the advantages of the more expensive lights? Ans. The more expensive lights are set up as a parallel circuit while less expensive lights are set up in series. As a result, when a bulb burns out in the series lights, all the remaining lights go out. When a light bulb burns out in the parallel Christmas lights, the remaining bulbs stay lit!

Assignment Practice Problems 6 and 7 p. 537 Practice Problems 6 and 7 p. 537 Practice Problems p. 540 Practice Problems p. 540