1. Electrical Energy
Chapter 13
Section 3

2. Series Circuit
A series circuit is a circuit that has only one loop for the current to flow through
Series circuits are used in flashlight and some Christmas lights
If any part of the circuit is disconnected, the whole circuit is open
When on light goes out, they all go out.
The current is the same throughout the entire circuit
The total resistance in the circuit is equal to the sum of the individual resistances.

3. Parallel Circuits
When you shut of one light in your house, do all the lights go out?
No…because houses are wired as parallel circuits not series circuits
Parallel circuits contain two or more branches for current to travel through
The total current in the circuit equals the sum of the currents in its parallel branches.
More current will travel through the branches with the least amount of resistance

4. Circuit diagrams
Electric circuits, whether simple or complex, can be described in a variety of ways
An easy way to visualize a circuit is by drawing a circuit diagram
There are common symbols used to represent parts of a circuit

5. Let’s try one…

6. An another one…

7. Household circuits
Household circuits are mostly a combination of parallel circuits
The voltage difference is supplied by the generator at a power plant
In the US, the voltage difference is typically 120V
Some appliance require more voltage difference (240V)
Dryers
Stoves
As current increases, thermal energy increases
How do we protect you home from too much thermal energy
Coated wires
Fuses
Circuit breakers

8. Fuses and Circuit breakers
The fuse is part of the circuit
Contain a small piece of metal that melts if the temperature gets too high
The metal melting breaks the circuit
Must be replaced
Part of the circuit
Contains a piece of metal that bends when the current is large and too hot
Circuit breakers can be reset

9. Electrical Power
Electrical energy is being converted to many different types of energy
Fan
Electricalmechanical
Hair dryer
Electricalthermal
Light bulb
Electricallight
The rate at which electrical energy is converted to another form of energy is electrical power

10. Electrical Power
The electrical power used depends on the voltage difference and the current
Electrical power = current x voltage difference
P = I x V
Electrical power is often expressed in kW

11. Let’s try one…
The current in an electric clothes dryer is 15 A when it is plugged into a 240V outlet. How much power does the clothes dryer use?
3.6 kW

12. Another one…
A flashlight bulb uses 2.4 W of power when the current in the bulb is 08 A. What is the voltage difference? 3V

13. Electrical energy = electrical power x time
Power companies charge by the amount of electrical energy used rather than the electrical power used
Electrical energy is measures in units called kilowatt hours (kWh)
Electrical energy = electrical power x time
E = P x t

14. Example 1
A microwave oven with a power rating of 1200 W is used for 0.25 h. How much electrical energy is used by the microwave oven?
0.30 kWh

15. The Cost of Electrical Energy
To determine the cost of electricity you need to calculate the amount of electrical energy used by the energy rate charged by the power company.
For example, if a 100 W lightbulb is left on for 5 hours, what is the cost of the electricity if the company charges $0.10 per kWh?
First calculate the energy used
Then calculate the cost
$0.05

16. Example 2
A TV with a power rating of 200 W uses 0.8 kWh in one day. How many hours was the TV used that day?
4 hours