About Resistors

Resistors, one of the most used types of electronic components, come in many shapes and forms.

Some types may have resistance values printed on them,
                resistors have printed values

but most are color coded to indicate resistance values and ratings.
a variety
                of color coded resistors

The color code consists of several colored bands which indicate the resistance values of resistors in Ohms as well as the tolerance rating. Most resistors have four or five bands, but occasionally you may come across resistors with three or six bands.

There is also as special case, a resistor with one black band. This is a zero-ohm resistor, i.e. not really a resistor but rather a piece of wire with a body. It is shaped like a resistor so that it can be fitted into printed circuit boards by automatic machines, when a link lead is needed.

The most common types of resistor codings are explained here.

A note about power ratings. As time has gone by, resistors have become much smaller for a given power rating. Old resistors with a 1/4 watt power rating quite often resemble modern resistors with a 1 watt or 2 watt rating, size wise. Be careful, bear that in mind when using or replacing old resistors.

Why use words rather than formulae?


One thing I had trouble with when I was young was remembering formulae.

If you ask most people to state Ohm's law, they will say V = RI or something similar.

I found it easier to remember as a sentence - "the voltage is directly proportional to the product of the current flow and the resistance", or "the resistance is directly proportional to the voltage applied and inversely proportional to the current flow", ie. R = V / I   .

The pages on this site work on that verbal principle. Read them slowly and carefully, and you might find you are understanding something for the first time, instead of merely applying the principles someone else has found to work.

The resistor color code page will tell you how to work out the resistance value.

Memorizing a statement can be easier than trying to remember a formula.  You just have to know how to construct the formula from the statement.  If you constructed the statement from studying the formula, that becomes very easy.

A Historic Note

Back in the 1950s I first encountered resistors. My cousin was a TV repair man, and he always had a few I could play with.  I made necklaces and chains with them. I didn't know I was being "kept occupied"!

Some of these resistors were prettier than others. They were colored all over. When I was older I realized these were "tip and dot" resistors. You might find a few in a really old radio, so I'm mentioning them. The other resistors had three colored bands around them, mostly on a white background.   

WTH something has to stimulate your interest! How to read a tip and dot resistor ... with the other color codes.