Mostly made of fixed capacity unchanged. The company is located in:

Variable capacitance; Capacitors can be freely adjusted within a certain range of capacity, such as; Radio can be manually tuned Channel selection is the use of variable capacitors

Adjustable capacitance (also known as semi-variable capacitance); Adjustable within a certain range of capacitors, such as; porcelain micro-carved capacitors and wound capacitors. The company is located in:

It can not be said that "a capacitor with large capacity has polarity". This is wrong, for example, the capacitor used to adjust the phase angle in the power system and arc extinguishing to be used in the starting circuit has a large capacity sometimes , But not polarity.