Source: All About Circuits (2012). Power in Electric Circuits. Retrieved 12 June 2012 from http://www.allaboutcircuits.com/vol_1/chpt_2/3.html
The power equation, often referred to as the Joule's Law, is a linear equation that relates the power dissipated in an electric circuit, the current, and the voltage. It is given as: where P is the power, I is the current, and E is the voltage. The power equation is applied in situations where electricity is used in our everyday life. Such situations, as described in the article, are heating, lighting, and traction among others.
In any electrical circuit, the power is directly proportional to the current flowing in the circuit. When there is no current flowing, i.e. when the switches are open, there is no power dissipated and no work is done. When the switch is open, an electric bulb does not give light. However, when the switch is closed, the bulb starts to give light and continues to brighten as the current flow increases. With an increase in the current flow, the power dissipated increases. This equation is the basis of the protective devices like fuses. When current flows through a fuse wire, power is dissipated in form of heat. As the current increases; more heat is dissipated, the wire becomes hotter and eventually melts, blocking further flow of current.
The article evaluates the equation in an acceptable manner. It gives real life applications of the equation and derives other important equations from the power equation. Also given are the mathematical examples of the applications of the equation and how to find any of the variables given two of the equation’s variables. It further relates this equation to the Ohm’s law equation which makes it even easier to find the variables of the equation.
