# Understand Resistor

resistor are utilized in the almost electronic circuit. come in a huge variety of shapes and sizes, and are available in a range of values that span milliohms to megaohms.

Ohm, the unit of resistance,  usually shortened as the Greek let er omega (Ω), although you will sometimes see the let er R used instead. For example, 100Ω and 100R both mean a resistor with a resistance of 100 ohms.

On a regular-hole resistor that has colored stripes on it, use the resistor color code. If your resistor has stripes in the same positions then the three stripes commonly on the left define the resistor’s value and the single stripe on the right determines the accuracy of the value.

Resistor Color Codes Table:

Image Source resistorguide

For a three-stripe resistor such as this, the first two stripes define the basic value and the third stripe defines the number of zeros to add to the end. In the example the value of a resistor with stripes red, purple, and brown  270Ω. I stated before that this line shows the number of zeros, but truly, to be more accurate, it  a multiplier. If it has a value of gold, then this means ⅒ of the value shown by the first two stripes. So brown, black, and gold would indicate a 1Ω resistor.

The band on its own defines the tolerance of the resistor. Silver indicates ±10%, gold ±5%, and brown ±1%. If your resistor has lines as shown in

then the value of the resistor defined with an extra digit of precision. In this case, the first three lines determine the basic value and the final digit of the number of zeros to append. This resistor also 270Ω.

## ≡  Select a Variable Resistor

A variable resistor, like a pot or potentiometer,  made from a resistive track and a slider that changes its position along the track. By changing the position of the slider you can vary the resistance within the slider and either of the terminals at the ends of the track. The most popular pots are rotary like the one shown

Pots come in a wide type of shapes and sizes.  shows a selection of pots.

The two pots on the left are called trimmers or trimpots.These devices designed to turned using a screwdriver or by twiddling the tiny knob within the thumb and forefinger. The next pot is a pret y regular device with a threaded barrel that allows the pot to fix into a hole. The pole can cut to the length wanted before fixing a knob to it.

There is a dual-gang pot in the middle his are really two pots with a common shaft and often employed in stereo volume controls. After that  a similar-looking device that joins a pot with an on/off switch. Finally, on the right a sliding type of pot, the kind that you might find on a mixing desk.

Pots are available with two kinds of tracks. Linear tracks become a close to linear resistance over the whole range of the pot. So, at the halfway point the resistance will be half of the full field.

Pots with a logarithmic track increase in resistance as a function of the log of the slider position first than in proportion to the position. This gives them more proper to volume checks as the human perception of loudness is logarithmic. Except you are making a volume control for an audio amplifier, you probably want a linear pot.

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