1. Electricity Physics 3: Current
Science 9
Electricity
Physics 3: Current

2. Objectives By the end of the lesson you should be able to:
Explain the difference between static and current electricity
Describe current
Know the 8 symbols for electric circuits

3. Remember…
Static Electricity is the build up of positive or negative charges

4. Moving Electrons
Because we can attract and repel electrons we can get them to move
Because we can move them we can get them to do work for us!!

5. Moving Electrons To make electrons move we need:
A source of electrons (i.e. a cell)
Something to attract or repel them (i.e. positive/negative terminals)
Somewhere for them to move to (i.e. copper wire)
THIS IS AN ELECTRIC CIRCUIT!

6. The 2 Variables
When electrons move through a circuit there are two things to keep in mind:
How many electrons are there?
How much energy do they have?

7. Number of Electrons
The amount of electrons flowing through a circuit is called the CURRENT
Current in measured in Amps (A) by an Ammeter
1 amp = 1 coulomb
sec
Remember a 1C = 6.24 X1018 electrons

8. Circuit Flow Electron Flow:
Electrons are repelled by negative end of cell
Electrons are attracted by positive end of cell
Electrons move from negative to positive
Conventional Current:
Flows from positive to negative
Doesn’t actually happen!!!

9. Drawing Circuits Always in a rectangular shape Must use a ruler
Lines represent wires
Use appropriate symbols to represent parts of the circuit
All circuits have: source, load, conductor, switch

10. Circuit Symbols Cell Light bulb Wires Ammeter Voltmeter Resistor
Fuse Open Switch Closed Switch A V