TODAY’S OUTCOMES:

- Review the concepts and definitions of current, voltage, power, and energy.

- Investigate the relationship between power, current, and voltage.

- Quantify the storage and release of electrical energy from a capacitor.

ELECTRICITY

In a water-siphon system, the analogous rule would be that the overall height between the source water and the dump location, regardless of the path or shape of the hose, is what determines the flow rate.

12. What would be the water analogy to the rule you gave (Q3)? Suppose you wanted to siphon water out of a fish tank quickly: what does the rule tell you?

Sample Q3 rule:

Brightness of bulbs in a series circuit increases with the number of batteries and decreases with the number of bulbs, and is not dependent on the sequence of the elements.

To quickly siphon a fish tank, maximize theheight difference between the aquarium waterlevel and the dump sink/bucket.

13. Duke Energy Company serves central North Carolina. It used to be called Duke Power Company. Most likely this name change was made for reasons that have nothing to do with physics, but let’s take them at their word: what were they selling before, and what are they selling now? Is it an energy bill or a power bill that you get at the end of the month?

A company selling “power” would be basing your bill on how quickly you use electricity, whereas a company selling “energy” would be basing your bill on how muchtotal electricity you use. In reality, an electrical company is generally only concernedwith your total usage, not the rate of your usage, so it is an energy bill you get at the end of each month.

POWER vs. ENERGY example:

If Person A runs a hair dryer for 5 minutes, and then Person B runs the same hair dryer for 20 minutes, both people used the same amount of power, but Person B used 4 timesas much energy.

Energy can be measured in killowatt-hours.Power = energy / timePower can be measured in kilowatts.

1 kilowatt = 1000 watts

.....so 1 kilowatt-hour is the amount of energy consumed by using 1000 watts for 1 hour.

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VOLTAGE ⇔ Height of the siphon system

CURRENT ⇔ Flow rate of the siphon system

Homework Assignment:

8. Rivers are dammed to make lakes. Sometimes the dam is used to operate a hydroelectric plant, which turns water power into electrical power. Use the internet to find the answers to these questions: What is the largest hydroelectric plant in the world?

What are the properties of a dam that represent the storage of a lot of energy?

What are the properties that will produce lots of power?

Three Gorges Dam in China on the Yangtze River. (22500 MegaWatts soon.....)

Itaipu Dam in Brazil is also an acceptable answer.

A large volume of water stored upstream, and also, a large difference in water level, or height of the dam, represents the storage of a lot of energy.

A hydroelectric dam is a lot like a huge siphon system!

Two factors contribute to the power produced:

1) A large flow rate through the dam will allow production of a large amount of power in the turbines.

2) The difference in height between the water source and outflow generates a greater push on the turbine blades.

This is essentially the same as the siphon systems we discussed.....

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VOLTAGE ⇔ Height of the siphon system

CURRENT ⇔ Flow rate of the siphon system

POWER ⇔ Increases with flow rate and height in a siphon system

- How to measure voltage and current in an electrical circuit using the appropriate device

- The difference between current and voltage in a circuit, and the analogous quantities in a siphon system

- The difference between energy and power, and their proper definitions in practical usage

WHAT YOU ARE EXPECTED TO KNOW:

TODAY’S OUTCOMES:

- Review the concepts and definitions of current, voltage, power, and energy. ✓

- Investigate the relationship between power, current, and voltage.

- Quantify the storage and release of electrical energy from a capacitor.

ELECTRICITY