This chapter is about resistors, the most basic electric component. Resistors are the most fundamental and commonly used of all the electronic components. All materials offer, to a certain degree, resistance to the flow of electrons. Metals, for example, offer very little electric resistance, but the resistance is there and it is not 0. There are two different symbols to represent a resistor in schematics, one in the American standard and the other in the international standard. The potentiometer is basically a three‐terminal device with a central axis that can be rotated or moved to make between its terminals. Trimpots or trimmer potentiometers are miniature potentiometers used for adjustment, tuning, and calibration in circuits. Resistors are the only components that behave the same way when connected to direct current or to alternating current.