Simple capacitor question
- Thread starter c1rcu1ts
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Depends. Your question is not clear. What is your application? Show us a circuit.
One does not usually charge a capacitor just for the sake of charging a capacitor except perhaps in a laboratory experiment.
A capacitor has many other useful functions in an electronic circuit, the least of which is just to put a charge in it.
One does not usually charge a capacitor just for the sake of charging a capacitor except perhaps in a laboratory experiment.
A capacitor has many other useful functions in an electronic circuit, the least of which is just to put a charge in it.
Application is just to charge a capacitor. (for my understanding)
Just wondering why in all of the circuits i have seen, they always put a resistor in series with the capacitor. In the charging equation V = Vo[1-e-(t/RC)] why not just put R = 0.
e-(t/RC) would eventually become 0 and Vo[1-0] = V (100% charged).
Basically why not just a capacitor and voltage source in series rather than a voltage source, resistor and capacitor in series.
Just wondering why in all of the circuits i have seen, they always put a resistor in series with the capacitor. In the charging equation V = Vo[1-e-(t/RC)] why not just put R = 0.
e-(t/RC) would eventually become 0 and Vo[1-0] = V (100% charged).
Basically why not just a capacitor and voltage source in series rather than a voltage source, resistor and capacitor in series.
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The RC circuits you see in the textbooks are for demonstrating the properties and behaviour of capacitors in an RC circuit.
You can connect the capacitor directly to a voltage source with no external resistor.
The exponential formula still applies but note that there is always a finite amount of resistance R in the circuit.
Hence the value RC still has some finite value. It is never zero. It means that the capacitor will reach full charge in a very short time.
But watch out. Calculate the peak current to the capacitor. You may be surprised how high it can be. A series resistor will lower the current.
You can connect the capacitor directly to a voltage source with no external resistor.
The exponential formula still applies but note that there is always a finite amount of resistance R in the circuit.
Hence the value RC still has some finite value. It is never zero. It means that the capacitor will reach full charge in a very short time.
But watch out. Calculate the peak current to the capacitor. You may be surprised how high it can be. A series resistor will lower the current.
To limit the current to an acceptable level.
On paper, the lack of a resistor would result in an infinite current for an infinitesimal amount of time. In a real circuit, there will always be some parasitic resistance, if nothing else, but it may be low enough that the resulting currents are high enough to cause problems. If so, then additional actual resistance needs to be added. If not, then call it good.
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