1. 8.2
Electric Current

2. The circuit
Electric Current – flow of charged particles (electrons) in a complete circuit.
Electric circuit – a complete pathway that allows electrons to flow.

3. Energy Around a Circuit
Electric Load – any device that transforms electrical energy into other forms of energy.
Examples: light bulb, buzzer, heater, motor
Figure Page 281

4. Circuit Components and Diagrams
Circuits are made up of four basic parts:
Source – source of electrical energy.
Conductor – the wire that 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 opening/closing the circuit.

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

7. 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
Drawing Circuit diagrams pg. 283 #1-3

8. Electrons are So pushy Electrons apply an action-at-a-distance force
This means electrons do not need to touch in order to push other electrons

9. Current Electricity and Static Charge
The charge in a battery is not an example of static electricity, even though the charge remains very nearly fixed on the battery terminals when the battery is not connected to a closed circuit
This continuous flow of charge in a complete circuit is called current electricity
Electrons travel only about 0.5mm/s in a circuit

10. Current: The measure of Flow
Is defined as one coulomb of charge passing a given point per second.
The flow of electrons from the negative terminal to the positive terminal through a wire (due to the difference in voltage between the positive and negative terminals).
Unit of Current – amperes (A)
Ammeter – used to measure the electric current flowing in wires.

11. 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!!!
Ben Franklin

15. 8.2 – Circuits extension

16. Objectives By the end of the lesson you should be able to:
Distinguish between (and draw) series and parallel circuits
Calculate current and voltage in all circuits
Convert between amps and milliamps

17. Types of Circuits There are two types of circuits:
Series: electrons can only flow along one path
Parallel: electrons can flow along more than one path

18. Series Circuits Can be recognized because there are no “intersections”
Current is equal everywhere
IT = I1 = I2 = I3 …
Voltage is equal to the sum of the voltages of each dry cell
VT = V1 + V2 + V3 …

19. Parallel Circuits
Can be recognized because there are “intersections” and the electrons have to make a “choice”
Current is equal to the sum of the current in each possible pathway
IT = I1 + I2 + I3 …
Voltage is equal everywhere
VT = V1 = V2 = V3 …

20. Ammeters and Voltmeters
Ammeters are put into circuits in SERIES
Voltmeters are put into circuits in PARALLEL

21. Summary
Series:
Total voltage is the sum of the voltage of each dry cell
Current is the same at every point in the circuit
Parallel:
Voltage is the same in every path
Total current is the sum of the current in each path