Homework from last class:• Answer the following questions:• “What is an electric circuit?”• “What is an electric load?”• “Explain how an electric circuit is like a

person going down a waterslide.”• Read over class notes and check class blog

http://www.msoonscience.blogspot.com

Chapter 8.2 pp. 280-288Electric Current

Electric CircuitElectric circuit: A complete pathway that allows electrons

to flow

Electric load: Any device that transforms electrical energy into other forms of energyex: a light bulb, buzzer, heater, and flashlight

pp. 280 - 281

A Simple Circuit:A Battery, Conducting Wires, and a Buzzer

p. 280

1) Chemical energy in battery gives electrons on the –ve terminal electric

potential energy

2) Electrons are attracted to the +ve terminal and are pushed through the conducting wire to the

buzzer

3) In the buzzer, the electrons’ potential energy is transformed into

sound energy

4) Electrons travel back to

the battery through the

complete circuit

p. 281

Circuit Components and DiagramsCircuits are made of only 4 basic components:

p. 282

Source: the source of electrical energy

Conductor: the wire through which electric current flows

Load: a device that transforms electrical energy into other forms of energy

Switch: a device that can turn the circuit on or off by closing or opening the circuit

source conductor

load

switch

Circuit Components and DiagramsCircuit diagram: a drawing using symbols to represent the

different components of a circuit

p. 282

Circuit DiagramsSimple to read diagrams should meet the following

criteria: Draw your diagrams using straight lines. Make all connecting wires and leads straight lines

with 90° (right angle) corners If possible, do not let conductors cross over one

another Your finished drawing should be rectangular or

square

p. 282

Circuit Drawing Time!1) Complete activity 8-2B Drawing Circuit Diagrams on p. 283.

Identify which circuits are closed and which ones are open. • A closed circuit has no breaks in the path of electrons.• An open circuit does not allow a flow of electrons because there is

a break in the path.

Electron Flow• As soon as a battery is

connected to a circuit, the circuit is closed.

• Electrons do NOT need to touch in order to push other electrons▫ Electrons apply an action-

at-a-distance force.

p. 283

Current electricity: the continuous flow of charge in a complete circuit

Current electricity is NOT the same as static electricity (charge that remains stationary on an insulator)

Electric CurrentElectric current: the amount of charge passing a point in a

conductor every second.Ampere (A): unit for measuring electric current; very small

currents are measured in milliamperes (mA)1 A = 1000 mA

Ammeter: a device used to measure the current in a circuit

p. 284

Ammeter symbol on a circuit diagram

Conventional Current• The flow of electricity is from

negative to positive (the flow of electrons).

• In the early days of electricity research, scientists mistakenly believed electricity flowed from positive to negative.

• Descriptions of this flow from positive to negative still existstoday, and is known as conventional current.

p. 284

Conventional current

Flow of electricity

Homework for next class:• Complete “Drawing Circuit Diagrams” and “Circuit

Symbols” worksheet (both sides)• Read over class notes and check class blog

http://www.msoonscience.blogspot.com

Works CitedImages taken from the following sources:http://zone.ni.com/devzone/cda/tut/p/id/7114http://iss.cet.edu/electricity/pages/b14.xmlhttp://schools-demo.clipart.com/search/index?q=buzzer&a=c