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A resistor is an electrical component with two terminals that is used to limit or regulate the flow of electrical current in electronic circuits. Its purpose is to reduce current flow as well as lower the voltage levels in its general vicinity or portion of the circuit. A resistor is meant to regulate the actual load on the system, meaning that it uses up electricity and dissipates it as heat, thereby effectively reducing the amount of electricity flowing out of it by specific amounts.
The resistor is one of the most important components in an electronic circuit as it allows the designer to precisely control the amount of current and voltage flowing at certain areas in the circuit. Therefore, it is an absolute requirement to ensure that sensitive electronic components such as integrated circuits (ICs) receive the precise amount of power that they require and nothing more, as an incorrect load often leads to degradation or outright burnout of ICs.
A resistor, though very small, is often made up of copper wires coiled around a ceramic rod and an outer coating of insulating paint. This is called a wire-wound resistor, and the number of turns and the size of the wire determine the precise amount of resistance. Smaller resistors, those that are designed for low-power circuits, are often made out of carbon film, which replaces the wound of copper wire, which can be bulky.
The outside of the resistor is marked by three bands of different colors equidistant to each other and a fourth band slightly farther from the third compared to previous spacing. The combination of the colors represents the value of the resistor in ohms. The bands are read from left to right, with the first two color bands representing the base value as individual digits, while the third is a power multiplier and the last is a tolerance indicator because manufacturing process limits the preciseness of the value. If there are five bands, then the first three represent the base value, whereas the last two still represent the multiplier and tolerance, respectively.
Color value representation: