Resistors are made by coating or winding the above-mentioned materials on a ceramic skeleton and externally coating paint to lead out pins (for thin film resistor materials, the surface after coating is etched with spiral lines).
For general fixed resistors, the surface coating is scraped off with a blade. Black is carbon film resistance, white is metal film resistance, or metal film resistance. Metal film resistance is better and more durable than carbon film resistance because of its high precision and large voltage and current (that is, high power and small heat generation). So that the circuit works more stably.