Tuesday, September 14, 2010

Notes from Page 553-563

Here are my notes for the pages 553-563.

-The amount of current flow in a circuit, and therefore the amount of energy transferred to any useful device depends on two things:
1. The potential difference of the power supply (amount of push)
2. the nature of the pathway through the loads that are using the electric potential energy.

-The more difficult the path, the more opposition there is to a flow.



-The measure of the opposition of flow is called electric resistance.

To measure resistance:

R=V/I

where R is the resistance in volts/ ampere (ohm)
V is the potential difference in volts
I is the resulting current in amperes

-A thinner wire has a larger resistance than a thicker one.


-Ohm found that the V/I ratio was constant for a particular resistor. This law is called the Ohm's Law.

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 Factors that Affect Resistance

-The longer the conductor, the greater the resistance. Factor: Length

-The larger the thickness of the conductor, the less resistance there is. Factor: Cross-sectional area

-Some materials are better conductors than others. Factor: Type of material
-Higher temperatures tend to increase the resistance. Factor: Temperature
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Kirchhoff's current law: The total amount of current into a junction point of a circuit equals the total current that flows out of that same junction.

Kirchhoff's voltage law: The total of all electrical potential decreases in any complete circuit loop is equal to any potential increases in that circuit loop.

-In any circuit, there is no net gain or loss of energy or electric charge.

Here are some links I found helpful:
1. http://www.the12volt.com/ohm/ohmslaw.asp
2. http://cnx.org/content/m0015/latest/
3. http://physics.about.com/od/electromagnetics/f/KirchhoffRule.htm

Here is a video for Ohm's Law:
http://www.youtube.com/watch?v=_-jX3dezzMg

and one for Kirchhoff's Law:
http://www.youtube.com/watch?v=Mc_g26ixTtA

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