MadSci Network: Engineering

Re: how can a capacitor discharge current into a bulb so dimming is absent?

Date: Wed Oct 15 22:39:57 2003
Posted By: Martin Smith, Engineering, B.E., M.EngSc., Uni of Qld / airline pilot
Area of science: Engineering
ID: 1064472632.Eg

Your theory is basically correct.

You can use a battery to charge a capacitor, and then that capacitor can be discharged into a load.

When capacitators are used in things like rectifiers they are in fact doing just what you say. They store and then discharge energy to maintain a more even output voltage.

The charging and discharging rate of a capacitor depends on the size of the capacitor and the in series resistance. This is called the time constant. Have a look at this website for a calculator in which you can vary R and C and see what sort of time constants you can expect. You will see that for a low resistance devices you would need a pretty big capacitator to maintain a current flow for seconds. See: Charging a Capacitor

This site: has some general background theory on capacitors

Martin Smith

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