Investigating Capacitors - page 1
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: 1 of 9 pages: 1 2 3 4 5 6 7 8 9
Investigating Capacitors
By Hirantha Mallikaaratchi
Aim
Our experiment is to investigate any correlations between the charging of a capacitor in terms of voltage and time.
Research
Before I can carry out any experiments, I must do some research into what exactly I am investigating. This will help me to understand how a capacitor works, and how to create an experiment in order for me to get some good evidence to support any hypothesises and any theories revolving around how a capacitor’s charging speed can be influenced by voltage.
In a way, a capacitor is a little like a battery. Although they work in completely different ways, capacitors and batteries both store electrical energy. A battery has two terminals; chemical reactions produce electrons on one terminal and absorb electrons at the other terminal. A capacitor is a much simpler device, but it cannot produce new electrons, it only stores them.
A capacitor from a camera
Like a battery, a capacitor has two terminals. Inside the capacitor, the terminals connect to two metal plates separated by a dielectric. The dielectric can be air, paper, plastic or anything else that does not conduct electricity and keeps the plates from touching each other. You can easily make a capacitor from two pieces of aluminium foil and a piece of paper. It won't be a particularly good capacitor in terms of its storage capacity, but it will work.
In an electronic circuit, a capacitor is shown like this:
Capacitor
A capacitor is most simply defined as two conductors separated by a dielectric. It is easier to grasp the significance of this definition by looking at a commonly used model for a capacitor that is shown here.
A dielectric is a material that is a good insulator (incapable of passing electrical current), but is capable of passing electrical fields of force.
When you connect a capacitor to a battery, here’s what happens:
• The plate on the capacitor that attaches to the negative terminal of the battery accepts electrons that the battery is producing.
• The plate on the capacitor that attaches to the positive terminal of the battery loses electrons to the battery.
Once it's charged, the capacitor has the same voltage as the battery (1.5 volts on the battery means 1.5 volts on the capacitor). For a small capacitor, the capacity is small. But large capacitors can hold quite a bit of charge. You can find capacitors as big as soda
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