Simple question about capacitor

  • Thread starter Cetullah
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    Capacitor
In summary: It seems like substituting a "k" for a "t" would be the most accurate answer.In summary, it takes about 1.6 seconds for a capacitor to reach 80% of its maximum potential difference.
  • #1
Cetullah
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My friends, it is probably an easy one, but I don't know it and I have an exam tomorrow :X

Homework Statement


How much time does it take for a capacitor to reach %80 of its max. potential difference?

Homework Equations



Thats the part I m needing.

The Attempt at a Solution




Thank you for your help!
 
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  • #2
It depends on the charging circuit. If an ideal capacitor is attached to an ideal voltage source through a switch, when the switch is closed, the capacitor will charge instantaneously. Non-ideal devices will have some resistance which will affect the charging time.
 
  • #3
Hmm... I have translated the question from my test completely, and there isn't any other information given. So, does it mean that the question is incomplete?
 
  • #4
Cetullah said:
Hmm... I have translated the question from my test completely, and there isn't any other information given. So, does it mean that the question is incomplete?

As mentioned before, in real life, even if there are no components in the circuit but the capacitor, the circuit will always have some non-zero resistance. So, if you assume that the capacitor is charging through a resistor, you can then answer the question.

How long does it take for the capacitor to reach 80% of full charge in an *RC* circuit?
 
  • #5
Hi Cetullah! :smile:
Cetullah said:
How much time does it take for a capacitor to reach %80 of its max. potential difference?

That's like asking "How long is a piece of string?" :confused:

You have to know something about the capacitor (and the circuit it's in) to answer that!

Are you sure a "time constant" isn't given?​
 
  • #6
Hi tiny-tim :smile:

Yeah, that's a weird question, but that's what exactly writes on the paper.

Our teacher is a weird man anyways.

But I guess, if sufficient data were given, we would use the equation "Vc=V*(1-e^(-t/RC)), right?
 
  • #7
Cetullah said:
Hi tiny-tim :smile:

Yeah, that's a weird question, but that's what exactly writes on the paper.

Our teacher is a weird man anyways.

But I guess, if sufficient data were given, we would use the equation "Vc=V*(1-e^(-t/RC)), right?

That equation seems about right. The question I asked you in my previous post still stands. There is not reason why you cannot express an answer in terms of the time constant.
 
  • #8
i agree :smile:
 
  • #9
Oh cepheid, so you advice me to substitute the "t" with something like "kRC"?

Edit: Did so, and found one of the answers on paper "1.6"
 

What is a capacitor?

A capacitor is an electronic component that is used to store electrical energy in an electric field. It is made up of two conductive plates separated by an insulating material called a dielectric.

How does a capacitor work?

When a voltage is applied across a capacitor, the electric field between the two plates is established. This causes one plate to accumulate a positive charge and the other plate to accumulate a negative charge. The capacitor then stores this electrical energy until it is discharged.

What are the different types of capacitors?

There are many different types of capacitors, including ceramic, electrolytic, film, and variable capacitors. Each type has different characteristics and is used for different purposes.

How do I choose the right capacitor for my circuit?

The right capacitor for your circuit depends on the specific requirements and specifications of your circuit. Factors to consider include capacitance, voltage rating, and tolerance. It is important to consult a datasheet or seek the advice of an expert when choosing a capacitor.

Can a capacitor be used as a battery?

No, a capacitor cannot be used as a battery. While both store electrical energy, a capacitor releases its energy quickly while a battery releases its energy slowly over a longer period of time.

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