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!Parallel | !Parallel | ||
|---- | |---- | ||
|V<sub>T</sub>=V<sub>1</sub> | |V<sub>T</sub>=V<sub>1</sub> V<sub>2</sub> … | ||
|V stays same | |V stays same | ||
|---- | |---- | ||
|I stays same | |I stays same | ||
|I<sub>T</sub>=I<sub>1</sub> | |I<sub>T</sub>=I<sub>1</sub> I<sub>2</sub> … | ||
|---- | |---- | ||
|R<sub>T</sub>=R<sub>1</sub> | |R<sub>T</sub>=R<sub>1</sub> R<sub>2</sub> … | ||
|1/R<sub>T</sub>=(1/R<sub>1</sub>) | |1/R<sub>T</sub>=(1/R<sub>1</sub>) (1/R<sub>2</sub>) … | ||
|---- | |---- | ||
|} | |} |
Revision as of 22:10, 10 April 2007
Some basic definitions, equations and analogies of electricity.
Definitions
Symbol | Unit | Description | Water Analog | Elec. Units | Base Units | |
---|---|---|---|---|---|---|
Voltage | V | volt (V) | Pressure (Potential) difference due to charge difference | Head: Pressure (Potential) difference due to height difference | J/C | kg•m²/(s³•A) |
Current | I | amp (A) | Flow of charge in charge/time or colombs/sec | Flow: Flow of water in volume per time such as liters/sec | C/s or W/V | A |
Resistance | R | ohm (Ω) | Opposition to the flow of charge | Friction: Opposition to the flow of water | V/A | kg•m²/(s³•A²) |
Power | P | watt (W) | Energy/Time = Power=Current*Voltage | Power: Power=Current*Pressure | J/s or A•V | kg•m²/s³ |
Energy | E | watthour (Wh) | The ability to do work | Energy: The ability to do work | 3600 J | kg•m²/s² |
Equations
- P=IV
- Power=Current*Voltage
- look familiar see P=Q*H*e/k
- V=IR
- Volts=Current*Resistance
- I=V/R might be more edifying since current is usually the result of pressure acting on resistance.
- This only applies to ohmic circuits, those circuits which display a linear relationship between current and voltage (i.e. the resistance does not change based upon current or voltage).
Series | Parallel |
---|---|
VT=V1 V2 … | V stays same |
I stays same | IT=I1 I2 … |
RT=R1 R2 … | 1/RT=(1/R1) (1/R2) … |
Analogies
The following animated analogy has much information to go along with it. This analogy is a combination of many analogies, and although has the problems endemic to all models, I feel that it is quite good. Please leave feedback, questions and lambastings on the discussion tab above. Look for an update in February 2007.
Water Tank - Electricity Analogy | |
---|---|
Component | Analog |
Tank | Battery |
Tank Vertical Difference | Battery Voltage Difference |
Water Flow | Electrical Current |
Mechanical Energy Appliance (Blender) | Electrical Energy Appliance |
Power=Head*Flow | Power=Voltage*Current |
For each example, ask yourself:
- How fast will the battery run out?
- How fast will the virgin margaritas be made?
- And most importantly why?
If you would like to do math to support these analogies, use:
- Feet = volts
- GPM = amps
- Each blender has a resistance of 6 Feet/GPM = 6 ohms
1 Tank 1 Blender
- This is the test case (datum).
1 Tank 2 Series Blenders
Notice that:
- The flow is 1/2 the speed of our test case.
- The two blenders in series are each going 1/4th the speed of our test case.
1 Tank 2 Parallel Blenders
Notice that:
- Each blender is at the same speed as our test case.
- The flow from the tank is twice as fast as our test case.
2 Parallel Tanks 1 Blender
Notice that:
- The blender is the same speed as our test case.
- The flow from each tank is half as fast as our test case.
2 Series Tanks 1 Blender
Notice that:
- The blender is 4 times the speed as our test case.
- The total flow is twice the speed as our test case.
Links
- http://www.uuhome.de/william.darden/
- Everything you every wanted to know about Lead Acid batteries.
- Car and Deep Cycle Battery FAQ
- http://hyperphysics.phy-astr.gsu.edu/hbase/electric/dccircon.html#c1
- Fantastic site on physics in general. Easy to understand, but accurate information on DC Circuits.
- HyperPhysics - DC Circuits
- http://library.thinkquest.org/10796/ch11/ch11.htm
- Some easy to follow basic theory.
- Lesson 3: Electricity - Colegio Franklin Delano Roosevelt
- http://science.howstuffworks.com/electricity.htm
- Some more information on electricity. Not wrot with error like at least one of their other pages.
- How Stuff Works - Electricity
- http://cnx.org/content/m1000/latest/
- Understanding current