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NORA Oilheat Technicians Manual

Chapter 8—Basic Electricity 8-5 electric heaters for toasters, electric water heaters, and electric baseboard heat. This heat can also be used to make heat anticipators in thermostats and safety timers in Figure 8-2: What’s a Watt? Did you know? Electric company bills are based upon kilowatts per hour, kwh. A kilowatt is 1,000 watts. Chapter 8 Basic Electricity The math Volts, amps, ohms and watts are all related to each other. If you change one, you change the others, too. These relationships are described by two math formulas: volts = amps times ohms and watts = volts times amps Remember, if one changes, it affects the others. 1 Volt 1 Amp 1 Watt primary controls. What’s a watt? Watts are the power consumed by an electrical circuit. One amp (remember, that’s the amount of flow) driven by one volt (the amount of pressure) through a circuit equals one watt of power, see Figure 8-2. This work can also be called horsepower. One horsepower equals 746 watts. If a circuit using one watt operates for an hour, this called a watt-hour. Sometimes, AC power is called volt-amps (VA) or apparent power. As current or voltage increases in a circuit, the power consumption and work done also increases. Every electrical device needs a certain amount of power, so it is given a power rating based on it being supplied with a specific number of volts and amps. If the right amount is not supplied, it changes the device’s power consumption and performance. Conductors Some materials offer very little resistance to the flow of electricity; these materials are called conductors. Most metals are good conductors. Gold, silver, copper, and aluminum are very good conductors. That’s why wires are made out of metal. Also, some switches are made out of mercury (a liquid metal). Wires are the conductors; they are very much like pipes for water. In a water pipe, not only does the pipe material affect the resistance to flow, the size of the pipe or wire also determines how much resistance to the flow there is. A fat wire, like a fat pipe, offers less resistance than a skinny one, and a short wire offers less resistance than a long one. In electricity, temperature is important, too. Cold conductors offer less resistance than hot ones. Force is needed to overcome this resistance. Remember, in water, the force is called pressure (pounds per square inch), and in electricity, the force is measured in volts. Insulators Many materials offer a lot of resistance to the flow of electricity, these materials are called insulators. Air, glass, porcelain, plastic, and rubber are all good insulators. They stop the flow of electricity. These


NORA Oilheat Technicians Manual
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