Resistors
A resistor is used to resist the flow of an electric current, and converts it to heat. Resistance is measured in ohms (
). The greater the resistance, the smaller the current that flows throught the resistor. Variable resistors are resistors that can change their resistance. They are used in devices such as volume controls, or the left-right balance in a stereo. In a volume control though, you would use a rheostat, and in the left-right balance you would use a potentiometer. A tapped resistor, is somewhat like a variable resistor that is fixed. It is tapped somewhere in the middle, and if the two ends of the resistor are A and C, and the middle lead that is tapping into the resistor is B, then the resistance of AC= the resistance of AB + the resistance of BC. But this does not necessarily mean that the resistance of AB = the resistance of BC, although it is a possability.
Because a resistor generates heat, the same schematic symbol is used for heating elements, such as in toasters.
Some resistors are shown above.
Water Analogy
A thin tube or pipe is similar to a resistor, because it slows down the flow of water (decreases current). The thinner the tube or pipe the higher the "resistance". A variable resistor is like a tube with a clamp on it that can be tightened or loosened, and is also similar to a faucet or valve.
Related Topics: Resistor Color Chart
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