A resistor is commonly referred to as a resistor in everyday life. It is a current-limiting element. When a resistor is connected to a circuit, the resistance value of the resistor is fixed, usually on two pins, and it limits the amount of current that can pass through the branch circuit to which it is connected. The resistance value cannot be changed is called fixed resistor. Those with variable resistance are called potentiometers or variable resistors.
The ideal resistor is linear, i.e., the instantaneous current through the resistor is proportional to the applied instantaneous voltage. Variable resistors for voltage division. One or two removable metal contacts are pressed against a bare resistor body. The position of the contacts determines the resistance between either end of the resistor body and the contacts.
The end voltage and current have a definite function relationship, reflecting the ability to convert electrical energy into other forms of two-terminal devices, denoted by the letter R, the unit is ohms