Custom Search
If you want to discuss more on this or other issues related to Physics, feel free to leave a message on my Facebook page.

## Thursday, December 16, 2010

### Errors and uncertainties

Rules to perform mathematical operations

lg and ln

Uncertainty and errors

Multiplication and division

root, powers, etc

Errors

What is an error?

What is a zero error?

What is a parallax error?

## Wednesday, December 15, 2010

### Current electricity

What is a complete circuit?

What is an ammeter?

What is the electromotive force (e.m.f.)

What is the potential difference?

What is the kilowatt-hour?

What is the voltmeter?

### What is a capacitor?

A capacitor is simply an device that is composed of two metal conductors that are separated by an insulator. The insulator is called a dielectric. Fig 1 below shows a simplified version of a capacitor.

Fig 1

In fig 2 below two metal foils are separated by a paper dielectric. The three are them are then rolled as shown.

Fig 2

The fig 3 below shows a capacitor as sold commercially. It is a capsule that contains the rolled up aluminium foils.

Fig 3

The two plates are then connected to a power supply. The positive plate is connected to the positive terminal while the other negative plate is connected to the negative terminal as shown in fig 4 below.

Fig 5

After the capacitor is connected to the power supply, the capacitor will be charged by the power supply. That is charges will accumulate on the two plates. Positive charges will accumulate on the positive plate of the capacitor while negative charges will accumulate on the negative plate of the capacitor. The charges on the two plates will create an electric field between the two plates where the energy will be stored in the form of electric potential energy.

The fig 6 below shows a capacitor whose terminals are connected to a light bulb.

When this happens the energy stored in the capacitor will be released i.e  is “discharged” into the bulb.

Fig 6

Hence a capacitor can be simply said to be an electronic device that stores charges. It is used in rectification circuits that changes alternating current to direct current, in tuning circuits and in filter circuits to filter out direct current.

### Capacitors

What is a capacitor?