A variable resistor, also known as a rheostat, is a type of resistor whose resistance value can be manually adjusted to meet the requirements of a circuit. Variable resistors can be classified into many different models and types based on factors such as their resistance values, adjustment ranges, adjustment mechanisms, manufacturing processes, materials used, and physical sizes. These include electronic component variable resistors, ceramic-disc variable resistors, surface-mount variable resistors, wire-wound variable resistors, and more. The nominal value of a variable resistor refers to the maximum resistance value that it can be adjusted to. In theory, the resistance value of a variable resistor can be adjusted to any value between 0 and its nominal value. However, due to practical structural limitations and precision design requirements, it is often difficult to achieve this "arbitrary" adjustment 100%. Instead, variable resistors typically allow for adjustments "basically" within an acceptable range, thereby enabling changes in resistance value.

　　Next, let’s talk about the 6 things you must pay attention to when using adjustable resistors!

　　① Before use, first check the quality of the adjustable resistor. The shaft and knob of the adjustable resistor should rotate smoothly and with appropriate tightness, and there should be no mechanical noise. Use a multimeter to verify that the nominal resistance value meets the specified requirements.

　　② Since some components of the adjustable resistor are made from synthetic resins such as polycarbonate, avoid using it in environments with high concentrations of chemicals—including ammonia, amines, alkaline solutions, aromatic hydrocarbons, ketones, and halogenated hydrocarbons—to prolong the service life of the adjustable resistor.

　　③ For adjustable resistors with grounded solder tabs, the solder tabs must be grounded to prevent external interference.

　　④ Do not operate the adjustable resistor beyond its rated load; always use it within its specified rating. When using an adjustable resistor as a variable resistor to regulate current, the allowable power dissipation should decrease proportionally with the travel distance of the moving contact’s brush, ensuring that the current flowing through the resistor does not exceed its rated maximum value and preventing the resistor from failing due to localized overloading. ⑤ The voltage drop generated when current flows through an adjustable resistor with a high resistance value must not exceed the resistor’s maximum allowable operating voltage.

　　⑥ To prevent the contacts and conductive layers of adjustable resistors from deteriorating or burning out, the operating current of low-value adjustable resistors must not exceed the maximum allowable current for the contacts.