Some substances, like carbon, conduct electricity fairly well but not that well. The conductivity can be changed by adding impurities like clay to a carbon paste, or by simply winding a thin wire as a coil. Electrical components made in this manner are called as resistors. They are very significant in electronic circuits as they allow for the control of current flow.
Resistors are manufactured to attain the exact characteristics. Imagine telling each person in the line that they should pass a certain number of balls per minute. This is analogous to creating a resistor with the certain value of electrical resistance. The better a resistor conducts, the lower will be the resistance of it; the worse it conducts, the higher will be the resistance.
Electrical resistance can be measured in units called ohms. For wires, the resistance is sometimes measured in terms of ohms per foot or ohms per kilometer. In an electrical system, it is desirable usually to have as low a resistance, or ohmic value, as possible. This is because the resistance converts electrical energy into heat. Thick of the wires and high voltages reduce this resistance loss in the long-distance electrical lines. This is why such huge towers, having dangerous voltages, are essential in large utility systems.
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