Just the Facts
Power: It's basic unit is the Watt, named after James Watt, the inventor of the modern steam engine. A watt is the unit for rate of conversion of energy (J/s). The power rating of an appliance tells how much and how quickly electical power is converted to light, heat, sound, or mechanical energy. The higher the power rating, the more 'powerful' the appliance is and the more energy it will consume. Electric companies bill by the kilowatt hour.(kWh). Potential Difference: It's the measurement of the change in electrical potential energy. Voltage (V) is the unit of potential difference. Potential difference may be measured after each component of a circuit or at the power source terminals to measure total circuit voltage. [V=I*R] Current: It's the rate at which electric charges move through a given area over a defined period. Current is measured in Amperes (I), or simply Amps (I). Current moves faster through improved conductors. For example current will move more easily through a thick, gold wire than through a thin, copper wire. [I=V*R] Resistance: The ratio between potential difference and the current carried in a circuit is resistance. Resistance is measured in Ohms, written with the Greek Omega symbol, or as the variable 'R'. Every component of a circuit has a slight resistance to the current provided by the power source. Large ticket items hooked up to the circuit such as light bulbs, appliances etc. are large power drains; hence, they are a large resistance source on a circuit. Smaller items, such as specific resistors, are used to step down current to run items with a lower power rating than supplied by the power source. These are designed to be inefficient and waste energy by providing a difficult path for electrons. The excess energy is often released as heat. [R=V*I]
