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How does a capacitor store charge? And how is it utilised by us?

How does a capacitor store charge?


 And how is it utilised by us?

Grade:12

1 Answers

Sher Mohammad IIT Delhi
askIITians Faculty 174 Points
9 years ago
The capacitor essential made from two metal plates separated by a distance with a material called the dielectric in the between which typically is an insulator material - it does not conduct electricity.
When charged (by a battery for example) it stores a charge the plates (electrons). This creates an electric field between the plates of the capacitor. The electric field has an energy associate with it.
The situation with the charge on the capacitor is like a ball held at a certain height, h, above the ground in gravity. It has potential energy equal to mgh in the gravity field. When you release the ball it drops and the potential energy is converted into kinetic energy.
For the capacitor, the electric charge the plate sets up an electric field between the two plates. The electric field holds potential energy. When a load (resistor or a motor) is attached to the plates of the capacitor, it discharges the charge and converts the potential energy stored in the electric field, into electric energy that drives electrons through the resistor or motor. If is is a motor it does work on the motor which is converted into mechanical energy. If it is a resistor, it heats up the resistor.
It has a limit, because as you added more charge, the electric field in between the plate be comes more intense. You measures this by the strength of the voltage between the plates. At some point the voltage will cause a break down in the dielectric, i.e. it no longer can insulate well, and the electric will discharge across the plate. It's like lightning between the clouds and the Earth. As long is the voltage is low enough the air acts as a insulator. If enough charge accumulates in the clouds and the voltage exceeds the breakdown voltage of the air, there is a breakdown of the insulating property of the air and you have lightning. The energy stored between the clouds and Earth is discharged via the lightning. So the clouds and the Earth acts like a big capacitor.

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