Archive:Principles of Electricity: Difference between revisions
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'''Basic formulas calculating resistance, | '''Basic formulas calculating resistance, current, voltage, and power-''' | ||
<br> | <br> | ||
where: | where: | ||
<br> | <br> | ||
*V= voltage | *V= voltage (Measured in [[Wikipedia:Voltage|Volts]]) | ||
*I= | *I= current (Measured in [[Wikipedia:Electric_current|Amperes]]) | ||
*R= resistance | *R= resistance (Measured in [[Wikipedia:Electrical_resistance|Ohms]]) | ||
*P= | *P= power (Measured in [[Wikipedia:Electric_power|Watts]]) | ||
Ohm's Law | Ohm's Law | ||
<math>V=I*R</math> | <math>V=I*R</math> | ||
The definition of resistance requires us to regard it as a derived quantity. Resistance is associated with particular '''objects''' and not '''materials'''. For any device, we 'supply' a electric potential difference (voltage) and a current, and take the ratio of these two measured quantities to find resistance, as per 'Ohm's Law'. The elementary case of this law states that the relation is linear for all values of voltage and current, but this is not true. At high temperatures (generally, non-standard conditions) the linearity breaks down, in loose analogy to yield strength of a solid (continuum). | |||
<br> | <br> | ||
Power Law | Power Law | ||
| Line 17: | Line 20: | ||
<math>P=(V^2)/R</math><br> | <math>P=(V^2)/R</math><br> | ||
*note 2 values must be given to find unknown | *note 2 values must be given to find unknown | ||
[[Category:Electrical engineering]] | [[Category:Electrical engineering]] | ||
[[Category:Electricity]] | |||
Latest revision as of 08:19, 12 June 2009
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Basic formulas calculating resistance, current, voltage, and power-
where:
- V= voltage (Measured in Volts)
- I= current (Measured in Amperes)
- R= resistance (Measured in Ohms)
- P= power (Measured in Watts)
Ohm's Law <math>V=I*R</math>
The definition of resistance requires us to regard it as a derived quantity. Resistance is associated with particular objects and not materials. For any device, we 'supply' a electric potential difference (voltage) and a current, and take the ratio of these two measured quantities to find resistance, as per 'Ohm's Law'. The elementary case of this law states that the relation is linear for all values of voltage and current, but this is not true. At high temperatures (generally, non-standard conditions) the linearity breaks down, in loose analogy to yield strength of a solid (continuum).
Power Law
<math>P=V*I</math>
<math>P=(I^2)*R</math>
<math>P=(V^2)/R</math>
- note 2 values must be given to find unknown