Electric power
From Wikipedia, the free encyclopedia (18-Dec-2013)
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt, one joule per second.
Definition
Electric power, like mechanical power, is the rate of doing work, measured in watts, and represented by the letter P. The term wattage is used colloquially to mean "electric power in watts." The electric power in watts produced by an electric current I consisting of a charge of Q coulombs every t seconds passing through an electric potential (voltage) difference of V is
- Q is electric charge in coulombs
- t is time in seconds
- I is electric current in amperes
- V is electric potential or voltage in volts
(or I = Q (in coulomb) / t (in second), V = Energy (in joule) / Q (in coulomb), so P= (Q/t) x (Energy / Q) = Energy / time ---> the rate (in terms of time) at which electric energy is transferred)
:
:
Resistive circuits
In the case of resistive (Ohmic, or linear) loads, Joule's law can be combined with Ohm's law (V = I·R) to produce alternative expressions for the dissipated power:
-end of wiki quote
The difficulty to understand (if you try to understand these equations in stead of just to memorize these) comes form that these are all definitions.
1) Power is a definition.
P = IV
I multiplied by V. What does this multiplication mean ? No special meaning. This is a definition.
2) Work is a definition.
Work = P x time (= Energy). Mechanically F (Force) x l (length, distance).
3) Charge and the unit of charge - coulomb(s) - are definitions.
Charge = Current x time, 1 Coulomb = 1 Ampere x 1 second
4) Voltage and the unit of voltage - volt (s) - are definitions.
Voltage = Energy / Charge. 1 volt = 1 Joule / 1 coulomb
Meanwhile the following equations are not definitions but showing relations.
1) Ohm's Law
2) Capacitor
3) Inductor
Is Energy also a mere definition ?
sptt
No comments:
Post a Comment