Resistors & potentiometers
A resistor adds a fixed, known resistance to a path. That one trick covers a lot of jobs. It limits current so an LED survives. Two of them split a voltage into a smaller one. A resistor sets an amplifier’s gain, or holds a signal line at a known level when nothing else is driving it. When a circuit needs a specific current or a specific ratio, a resistor is usually what sets it.
Real resistors carry two ratings besides their value. Tolerance says how far the actual resistance can stray from the marked value; ±1% is normal for modern parts. The power rating says how much heat the body can shed. The tiny surface-mount resistors on most boards handle about a tenth of a watt, so anything dropping real power needs a physically bigger part.
A potentiometer is a resistor with a third terminal: a wiper that slides along the resistive track. Wired with all three terminals it forms an adjustable voltage divider, which is what a classic volume knob is. Wired with two, it’s just a variable resistor you can set by hand.
Key points
- Resistors limit current and set voltage ratios. Those two jobs explain almost every use.
- Tolerance (±1%, ±5%) is how accurate the value is; the power rating is how much heat it survives.
- Small SMD resistors typically handle around 0.1 W. Check the dissipation before assuming any resistor will do.
- A potentiometer’s wiper turns it into a hand-adjustable divider or a variable resistor.
Practice
0 of 2 answered · Not startedWrong answers just let you try again, and hints are there if you want them. Answering every question first time, without hints, is what earns mastery.
- 1
A 1 % and a 5 % resistor of the same value are otherwise identical. What does the tolerance tell you?
- 2
You wire a potentiometer using only the wiper and one end terminal. What have you built?
