1. Current Electricity

2. How is current produced?
When a high potential is connected by a conductive material to a low potential.
Flow of electrons is called electric current.
Units: C/s = Amperes (Amps)
Low Potential
High Potential
Equal Potential
Equal Potential

3. When the potentials are equal, the current stops flowing
Low Potential
High Potential
Electron Pump
When the potentials are equal, the current stops flowing
To increase the potential of the electrons an electron pump must convert (do work) another form of energy into electrical potential energy.
Electron pump examples:
Voltaic or galvanic cell (dry cell)
Several cells connected (Battery)
Photovoltaic cell (solar cell)
Generator
After slide do Inquiry for circuit (groups, light bulb, wire) Students draw circuit of light that lights.

4. Two types of current
Direct Current – (D.C.) Flow of electrons in only one direction
Battery
Alternating Current – (A.C.) Flow of electrons at first in one direction and then the other direction.
Generator
In your House
60 Hertz

5. What affects current flow?
Potential Difference – Voltage
Resistance - slowing or reduction of the flow of current
Resistance depends on the material, length of material, and the cross sectional area of the material through which the current is moving.
R is resistance, r is resistivity,
L is length, A is the cross sectional area

6. Ohm’s Law
Ohm’s Law stated – The ratio of V/I is a constant, where V is the voltage applied across a piece of material (such as wire) and I is the current through the material. R is the resistance of the piece of material.
Units: Ohms (W) = Volt/amp

7. Electric Power
When there is current (I) in a circuit as a result of a voltage (V), the electric power (P) delivered to the circuit is:
Units: watts = amp x volt = J/s

8. Electric Power
Many electrical devices become hot when provided with sufficient electric power. Toasters, irons, space heaters, heating elements in electric stoves, and incandescent light bulbs. In such cases it is possible to obtain two equivalent power equations
When electric energy is transferred into thermal energy in a resistor, the increase in thermal energy is:
units: Kilowatt hour or Joules

9. Current in electric Circuits
An electric Circuit is a closed loop.
Basic Circuits consist of three things:
Electron pump (Battery)
Device that reduces potential (User)
Conducting connections (Wires)

10. Direct Current Circuits:
Circuit – closed loop in which current can flow
Basic simple circuit
Voltage source
Voltage uses
conducting connections (wire)
Diagrams for electric circuits
Describe in words
use photographs/drawings
Use symbols (schematics)

11. Schematic Symbols

12. Drawing Schematic Circuits
Draw symbol for battery and indicate “+” and “-“ terminals
Draw wire from “+” to the voltage user and draw its symbol.
If a point where there are two current paths, draw connection symbol and follow one path to the user. Return to the second path and draw to its user and continue until paths join.
Follow path to the “-“ terminal
Check work
Connect ammeter in series
Connect voltmeter in parallel

13. Objectives Describe the configuration of a working circuit
Interpret circuit diagrams
Describe the characteristics of series connections
Determine equivalent resistance of circuits having two or more resistors.
Explain the cause of short circuits
Homework:
Read Pages
Pg 534 #1-3, Pg 537 # 6-9

14. Series Circuits Only one path for current to follow
User followed by another user (ie. Resistor followed by a light) …

15. Series Circuit Rules Current is the same for each user
The effective resistance is the sum of all resistors in the series
The sum of the voltage drop is equal to the total voltage drop

16. Parallel Circuits
Two or more paths for current to follow

17. Parallel Circuit Rules
Total current in the circuit is the sum of the current in all its paths (branches)
The equivalent resistance decreases with more parallel resistors
Voltage is the same in each path.

18. + -

19. Objectives Describe the configuration of a working circuit
Distinguish between series and parallel circuits
Describe the characteristics of series connections and of parallel connections.
Interpret circuit diagrams
Determine equivalent resistance of circuits having two or more resistors.
Explain the cause and prevention of overloading household circuits.
Homework:
Read Pages
Pg 534 #1-3, Pg 537 # 6-9