1. AC DC
Not the awesome, long-may-they-reign, Australian kings of the power chord ……..

2. Technology Wars
Why is alternating current used to supply electricity virtually everywhere in the world??? And not direct current?
Why iPod vs. Rio vs. Zune?
Why PC vs. Mac?

3. Typical reasons why one ‘wins’ over a competitor…
Possess key ‘enabling’ technologies
Better reliability, safety, ease of use, ability to meets customers’ long term needs
Public perception about reliability, ‘image’, safety, ease of use
More funding available or stronger backing from scientific community

4. The War of the Currents
Thomas Edison (proponent of direct current) and Nicolai Tesla funded by Westinghouse (of alternating current)
Addressed these issues through extensive research, public demonstrations and lectures, ‘news’ reports via newspapers

5. Direct current Thought of as supplied by batteries
Can also have DC powerplants
Always flows in one direction

6. Alternating current Electrons move back and forth Net motion is zero
BUT the transport of energy between the electrons is the important thing
Because it’s cyclic, there is another issue
Can be transmitted at various frequencies
In US, 120V and 60Hz for homes

7. Residential and commercial customer requirements
electricity of various voltages
Smooth delivery of power for running motors
People would prefer not to live close to powerplants, so electricity should be able to be transmitted over relatively long distances
Transmission should be efficient, not a lot of power loss from powerplant to customer
Might need both DC and AC

8. AC’s not perfect but it ‘won’ because….
AC can be transformed from higher to lower voltage and vice versa
Enabling technology: the transformer
AC provides ‘smoother’ flow
AC can be transmitted over long distances, at high voltages, therefore low power loss and transformed to low voltages, closer to the user
Easier to convert from AC to DC when needed than vice versa (stuff that runs on batteries can be plugged in to an outlet)

9. So, why the different types of plugs on different appliances?
Safety for appliances and wiring
A way to match the appliance with its required voltage and frequency
No way you can mix up a square peg (120 V plug) into a round hole (240 V)

10. Electrical Power Transmission
When transmitting electric power over long distances, it is most economical to use high voltage and low current
Minimizes I2R power losses
In practice, voltage is stepped up to about V at the generating station and stepped down to V at the distribution station and finally to 120 V at the customer’s utility pole

11. Follow the flow!

12. How does it get to my house?
Right outside your house, Voltage is transformed to 120V

13. Household Circuits
The utility company distributes electric power to individual houses with a pair of wires
Electrical devices in the house are connected in parallel with those wires
The potential difference between the wires is about 120V

14. How do you get 240v?

15. Household Circuits, cont.
A meter and a circuit breaker are connected in series with the wire entering the house
Wires and circuit breakers are selected to meet the demands of the circuit
If the current exceeds the rating of the circuit breaker, the breaker acts as a switch and opens the circuit
Household circuits actually use alternating current and voltage

16. Breaker panel
Your house?

17. What’s with that third prong? Ground Wire
Electrical equipment manufacturers use electrical cords that have a third wire, called a case ground
Prevents shocks