URGENT!!! Urgent!!! What kind of classification are wire-wound resistors....

Wire-wound resistor wire-wound resistor is composed of a resistor wire wound on an insulating skeleton. The wire is generally made of nickel-chromium, manganese-copper and other alloys with a certain resistivity. The insulating skeleton is made of ceramics, plastics, metal coated with an insulating layer and other materials in various shapes such as tubular and flat. Resistor wire in the skeleton according to the need to wind a layer, can also be wound multi-layer, or non-inductive winding method, etc..　This kind of resistance is divided into two kinds: fixed and variable. It is characterized by stable operation, good heat resistance, small error range, resistance value can be accurate to 0.001 ohm, more expensive, mostly used in medical equipment, rated power is generally more than 1 watt.　Wirewound resistors are accurate, theoretically speaking, unless the charger output voltage reference, general chargers do not use wirewound resistors. Charger circuit for SMPS switching power supply circuit, the high voltage end of the signal generating circuit is very high, it is not possible to use wirewound resistors, otherwise it will lead to self-excitation, which affects the oscillation frequency, thus making the output fluctuation is large, only the low-voltage end of the sampling reference circuit may use wirewound resistors.　Wear and tear will cause the local wire diameter to become thinner, and in the case of long-term use of energized, the long-term role of the current makes the intrinsic composition of the wire changes, thus making the resistance value smaller.