Investigating Capacitors - page 2
Keywords: Investigating Capacitors coursework GCSE physics
By slashwk on 23/11/2006 17:28:09
Level: GCSE Key Stage 4 (Years 10-11)
Page Number: 2 of 9 pages: 1 2 3 4 5 6 7 8 9
cans, for example, that hold enough charge to light a flashlight bulb for a minute or more. When you see lightning in the sky, what you are seeing is a huge capacitor where one plate is the cloud and the other plate is the ground, and the lightning is the charge releasing between these two "plates." Obviously, in a capacitor that large, you can hold a huge amount of charge!
Charged Capacitor
A capacitor is said to be charged when there are more electrons on one conductor plate than on the other. The plate with the larger number of electrons has the negative polarity. The opposite plate then has the positive polarity. When a capacitor is charged, energy is stored in the dielectric material in the form of an electrostatic field.
Like a Water Tower
One way to visualize the action of a capacitor is to imagine it as a water tower hooked to a pipe. A water tower "stores" water pressure -when the water system pumps produce more water than a town needs, the excess is stored in the water tower. Then, at times of high demand, the excess water flows out of the tower to keep the pressure up. A capacitor stores electron in the same way and can then release them later.
Let's say you hook up a capacitor like this:
Here you have a battery, a light bulb and a capacitor. If the capacitor is pretty big, what you would notice is that, when you connected the battery, the light bulb would light up as current flows from the battery to the capacitor to charge it up. The bulb would get progressively dimmer and finally go out once the capacitor reached its capacity. Then you could remove the battery and replace it with a wire. Current would flow from one plate of the capacitor to the other. The light bulb would light and then get dimmer and dimmer, finally going out once the capacitor had completely discharged (the same number of electrons on both plates).
Electrostatic Induction
When an electron is added to one plate of a capacitor, one electron is driven away from the opposite plate. Or you can say that when an electron is pulled away from one plate of a capacitor, another electron is drawn to the opposite plate. No matter how you look at it, this is the principle of electrostatic induction
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