Resistor

A true two-terminal resistor: Ohm's law, with no idea which way around it is wired.

It has no polarity and no special cases. Each pin is driven from the Thevenin equivalent seen at the other pin plus its own value, so the same part is a pull-up, the top half of a voltage divider, and the series resistor that keeps an LED alive, with nothing about the model changing between the three.

Pins

Pin	What it does
1	Either end. There is no "in" side.
2	The other end.

Properties

value: the resistance in ohms. 220 for an LED, 10 000 for a pull-up, whatever a divider or a timing network calls for.

What the model gets right

A resistor does not need a matrix to behave, so on its own it never creates an analog island. But when one reaches it (the series resistor of an RC network, the two timing resistors of a 555), it joins the island and is stamped as a conductance instead of passing a Thevenin equivalent along, and its current probe still reads the same current either way.

What it does not model

No tolerance, no temperature coefficient, no power rating. A resistor here will happily pass an amp through a quarter-watt value and simply report the current; it will not heat up, drift or fail open. No Johnson noise, no parasitic inductance or capacitance, and no preferred-value grid: any positive number is a resistor, where a real bin holds E12 or E24 values only.

Common mistakes

Reading the probe backwards: current is positive from pin 1 to pin 2, so a divider wired the "wrong way around" on the canvas still works, but the sign on the probe flips. And a resistor left out of an LED or a base-drive circuit is the single most common reason a beginner's circuit shows a very bright, very short-lived LED, or a transistor that never turns off cleanly. See the transistor.

See it in action

Every worked example on the site starts here. Hello, breadboard is the plainest one; Dark detector and RC filter on the scope put a resistor to work in a divider and a filter. The full set is at /templates.