Power resistance is a common resistor. In many cases, the volume of power resistance is closely related to power, and the larger the power, the larger the volume. But not all power resistors are like this. Power resistors are made of different materials or processes, and can not be judged by volume. For example, the same volume of metal film resistance and carbon film resistance, the former is more than twice the power of the latter.

In addition, the resistance value of the power resistance is not directly related to the power, which is easy to be confused. In many cases, it is easy to misunderstand the resistance, such as the carbon film resistance, which belongs to the thin film resistance. It is formed by deposition of a resistance film on a carbon rod substrate, the thickness of which is less than a few microns, so for this type of carbon film resistance, it is impossible to do much power. However, their resistance range can be done in a wide range of 0.5 Ω ~ 1MΩ.

In addition, the cement resistance is made by winding the glass fiber column with the resistance wire with low resistivity and enclosing the ceramic shell. The power range of this type of cement resistance is 2 ~ 15 W, the resistance value is in the range of 0.1 ~2200 Ω, and in some factories the power range of the cement resistance is in the range of 5 ~15 W and the resistance value is in the range of 0.1~2700 Ω. There are also other resistance manufacturers of cement resistance in the power range of 10~40 W, resistance in the range of 0.1 × 4 300 Ω.
 
If only in terms of the volume of the power resistance, the larger the volume, the power must be relatively large in it. Because power resistors emit a lot of heat and consume power when the current passes by, the manufacturers of the power resistors are calculated according to their rated resistance and power. Otherwise, it will cause the resistor to burning hot, scorch and even burn.
In fact, the volume of resistance is mainly related to power. The larger the resistance value, the smaller the current passing through. The lower the power, and the smaller the resistance value, the larger the current passing through, the greater the power, the more obvious the heating, and the easier it is to burn the resistance. And the larger the volume, the more convenient the heat dissipation. The relationship among resistance, volume and power has a certain effect. Heat-resistant power refers to the amount of heat dissipation that the resistor can withstand within a unit of time, in watt (W). Generally, the heat dissipation of the resistor is related to the heat dissipation condition, and the larger the volume of the resistor, the more easily the heat is emitted, so the larger the volume of the resistor of the same kind, the greater the heat-resisting power of the resistor.