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Capacitance
Demonstration
created by: Dr. Scott Dwyer - 2002
Modified
8/11/03
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CONCEPTS: |
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EQUIPMENT: |
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EXPLANATION: |
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The unit of capacitance is the "Farad". Typically,
capacitors come in "microfarad" and "picofarad"
sizes, although larger values are not uncommon. To demonstrate
the size of a capacitor, we charged capacitors of varying size
with a power supply and then discharged them through a light
bulb, watching to see how long the light bulb stayed lit.
| Capacitor Size |
Time Bulb Stayed Lit |
| 5000 micorfarads |
2 sec |
| 14,000 microfarads |
8 sec |
| 50,000 microfarads |
10 sec |
| 1 Farad |
135 sec |
The large 1 Farad capacitors are typically used in electronic
devices to protect against power failure, like your telephone
answering machine or laptop computer where the current draw
is far less than a light bulb. They can preserve your messages
or computer files for days.
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