1. Section 1 Electric Charge
Chapter 7 Electricity
Section 1 Electric Charge

2. Static Electricity Accumulation of excess electric charge
As you walk across the carpet, electrons are transferred from the carpet to your shoes
Your shoes become negatively charged
The carpet becomes positively charged

3. Law of Conservation of Charge
Charge can be transferred from object to object, but it cannot be created or destroyed.
Usually the electrons move from place to place

4. Forces and Electric Charge
“Like” charges repel
“Unlike” charges attract
This is why clothes from the dryer stick together due to the transfer of electrons

5. Electric Fields
There is an electric field around every electric charge
Example:
Being shocked when you reach for a doorknob but do not actually touch it

6. Conductors and Insulators
Conductors- electrons move through easily
Ex: Metals
Insulator- electrons do not move through this material easily
Ex: Plastics

7. Charging Objects
Charging by contact- charge is transferred by touching or rubbing
Charging by induction- charges are rearranged on a neutral object due to a nearby charged object

8. Explain why if charge cannot be created or destroyed, electrically neutral objects can become electrically charged.

9. Humid air is a better electrical conductor than dry air
Humid air is a better electrical conductor than dry air. Explain why you’re more likely to receive a shock after walking across a carpet when the air is dry than when the air is humid.

10. Section 2 Electric Current
Chapter 7 Electricity
Section 2 Electric Current

11. Electric Current This is the flow of electrons
Measured in amperes; amps
The rate that the electrons move through a conductor.

12. Voltage Difference
Related to the force that causes electric charges to flow
Measured in volts; V

13. Voltage Electric Charge flows from higher voltage to lower voltage
A.K.A. :
Potential Difference- the work that must be done to move a charge from one place to another

14. Circuit Closed path that current flows through
Current will only flow on a closed path

15. Resistance How much a material opposes the flow of electrons
Measured in ohms; Ω

16. Resistance Temperature Length *When these
Thickness increase so does resistance

17. Ohm’s Law
Equation
Current = voltage difference
resistance or
I= V R

18. Example
Calculate the voltage difference in a circuit with a resistance of 25Ω if the current in the circuit is 0.5 A.

19. Example
A current of 0.5 A flows in a 60 W light bulb when the voltage difference between the ends of the filament is 120 V. What is the resistance of the filament?

20. Section 3 Electrical Energy
Chapter 7 Electricity
Section 3 Electrical Energy

21. Closed vs. Open Circuit Closed Circuit: Charge can flow uninterrupted
Open Circuit: Charge cannot flow; circuit is broken

22. When one bulb is out in a string of lights, why do the rest not work??

23. Circuits Switch- used to open and close a circuit
- Ex: Light switch in your home
Schematic Diagram- a diagram that depicts the construction of an electrical circuit or apparatus

24. Series Circuit The current can only flow through one loop
Used in flashlights and holiday lights

25. Parallel Circuits
These have two or more circuits the current can move through
Used in houses and automobiles
Useful because unlike series circuits, individual parts can be turned off without affecting the entire circuit

26. Household Circuits
If too much current flows through the wires, they will overheat and melt which can cause a fire
To protect against this fuses and circuit breakers are used

27. Fuses
These contain a small piece of metal that will melt if it becomes too hot
This causes a break in the circuit which stops the flow of current
You must replace these with new ones

28. Circuit Breaker Contains a piece of metal that bends when it overheats
The bending causes a switch to flip which opens the circuit and stops the current flow
These may be reset by flipping the switch

29. Electric Power
How fast electrical energy is converted to another type of energy
This can be thermal, light, mechanical energy etc.

30. Electrical Power Equation
Electric power = current X voltage difference P= I(V) *Measured in watts; W *One kilowatt (kW) = 1,000 watts

31. Example
The current in an electric clothes dryer is 15 A when it is plugged into a 240 volt outlet. How much power does the clothes dryer use?

32. Electrical Energy Measured in kilowatt hours (kWh) Equation:
Electrical energy = electric power X time or
E= Pt

33. Example
A microwave oven with a power rating of 1,200 W is used for 0.25 h. How much electrical energy is used by the microwave?