Friday, May 09, 2008

Ohm's Law Wheel

Ohm’s Law Wheel. Power in electrical systems (P) is measured in watts. Resistive appliances such as a hair dryer or lightbulb are rated in watts. Power is computed as shown in the Ohm’s law wheel, in Figure 8.2.7. The relationships among power, current, voltage, and resistance are important to fire investigators because of the need to find out how many amperes were drawn in a specific case. See Figure 8.2.7 for a summary of these relationships. If, for example, several appliances were found plugged into one extension cord or many appliances were plugged into several receptacles on the same circuit, the investigator could calculate the current draw to find whether the ampacity of the conductor was exceeded.

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