A capacitor is a component which stores electric charge. The unit of capacitance is the Farad. However, 1 F is a very large capacitance. In most situations we use capacitors in the micro-Farad (µF) or nano-Farad (nF) range. Many capacitors can be connected either way but electrolytic capacitors (and some other types) are said to be polarised and must be connected the right way round. Nearly all "large" capacitors (greater than about 1 µF are electrolytic). Circuit symbols for capacitors are shown below.