Beginning Robotics – Resistors

If you have ever taken an electronic gadget apart, you have probably seen these guys:

This is a resistor.  From the name you might guess what a resistor does: it resists the flow of electric current.  Resistors are kind of like making the electricity squeeze through a narrow opening.  An electric heater is a giant resistor.  As the electricity tries to flow through it, the electrons all get crowded and rub against each other.  This generates heat.

The symbol for a resistor looks like a saw blade:

The amount of resistance that one of these gadgets has is measured in Ohms.  If a resistor has a lot of Ohms, it will keep a lot of electricity from flowing.  If you unplug a cord from the wall, the air in the room has so much resistance that no electricity will flow.

This is the symbol for Ohms:

It is the Greek letter omega.

A variable resistor is one that can change the amount of resistance it has.  This kind of resistor is often connected to a knob that a user can turn to control something.  Kind of like a dimmer switch can control how light a lamp is.  This is the symbol for a variable resistor:

You often use resistors in circuits when you don’t want the electricity to overpower some device.  Almost any electronics project will need resistors of some value.

If you are trying to figure out what the colors mean, see our Resistor Color Code Calculator.

Here are some common electronics components in their natural habitat…


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