This part has a page of its own, with a note on using it and a circuit to try: the part page.
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.
power: the power rating, from 1/8 W to 10 W. The common through-hole resistor, and
the default, is 1/4 W.
It burns
A resistor turns the power I² × R into heat. Run it far past its rating and a real
one chars, smokes and goes open circuit. In the editor the first time is a warning
(it glows amber and keeps working); the next time it burns, and a message says how
many watts it was turning into heat against its rating. It survives twice its rating held for ever
and heats with a time constant of half a second, so 10 ohm straight across 5 V
(2.5 W in a quarter-watt part) is gone in a fifth of a second, a short pulse is
not, and every pull-up, divider and LED resistor is thousands of times under. Pick
a bigger power for a load resistor, or press Run to start again with a new one.
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 and no temperature coefficient: its value does not drift as it warms. 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.
The resistor part page draws it live, with its pins and every project that uses one.