The action of a capacitor Capacitors store charge and energy. They have many applications, including smoothing varying direct currents, electronic timing circuits and powering the memory to store information in calculators when they are switched off. A capacitor consists of two parallel conducting plates separated by an insulator.
The lesson is complete and designed to be taught over a period of 90 minutes. It is fully animated and contains fully worked out answers to every question. Describe in terms of electron flow what is happening when a capacitor charges up Relate the potential difference across the plates of a capacitor to the charge on the plate
KEY POINT - The capacitance of a capacitor, C, is defined as: Where Q is the charge stored when the voltage across the capacitor is V. Capacitance is measured in farads (F). 1 farad is the capacitance of a capacitor that stores 1 C of charge when the p.d. across it is 1 V.
The higher the value of capacitance, the more charge the capacitor can store. The larger the area of the plates or the smaller their separation the more charge the capacitor can store. A capacitor is said to be “Fully Charged” when the voltage across its plates equals the supply voltage.
because the applied potential difference is shared by the capacitors, the total charge stored is less than the charge that would be stored by any one of the capacitors connected individually to the voltage supply. The effect of adding capacitors in series is to reduce the capacitance.
One of the most common applications of capacitors in large buildings is for power factor correction. When too many inductive loads are placed into a circuit, the current and voltage waveforms will fall out of sync with each other and the current will lag behind the voltage.