Energy stored in a capacitor works

In summary, capacitors store energy by creating a potential difference between the plates. The potential difference between the plates is reduced and hence capacitance is increased. However, if you charge a capacitor and then move a dielectric between the plates, the charge remains the same and the potential difference changes.
  • #1
hhhmortal
176
0
Im having trouble understanding how capacitors store energy. If a potential difference is applied to two parallel plates each with +-Q, it will set up polarisation charges on the dieletric between, which reduces the electric field inside the material. The potential difference between the plates is reduced and hence capacitance is increased.

But in terms of the electric field how does it store the energy?
 
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  • #2
Hi hhhmortal! :smile:
hhhmortal said:
Im having trouble understanding how capacitors store energy …

I don't see the problem…

a capacitor stores energy because opposite charges are on opposite plates of the capacitor …

they want to get together, but the absence of any connection stops them …

that's potential energy, because if you join the plates (either the quick way, or more usually the long way round via a circuit), the charges will move, and will do work in doing so. :wink:
 
  • #3
I also have had trouble with detailed descriptions dielectrics in capacitors, but then I am not a materials person, and so it doesn't matter much to me.

I will try to repeat the information of the previous reply in a different way.

An ideal capacitor has no real materials, neither for the plates, nor the dielectric. One may make a "real" capacitor with two plates, perhaps using a metal, but even in this case there is nothing wrong with the dielectric material being absent. In this case, the dielectric is the vacuum. Notice that the dielectric constant of any "real" dielectric (capacitor) is always a ratio of its permittivity compared to the vacuum.

Now, the vacuum is nothing, and so it has no polarization charges. The only charges "in the capacitor" are "on the plates". The entire electric field may be considered simply between these plates without further distraction.

If you should find enlightenment regarding how the polarization charges in a non-ideal dielectric contribute to its relative permittivity (an easy answer, that is), I am curious.
 
  • #4
Ok yea. The part which I don't understand is if you the dielectric constant is greater inbetween the plates, the capacitance increases. so by looking at equation:

CV = Q

Does this mean V between the plates must stay constant at all times hence the charges increase and thus amount of energy that the capacitor stores increases?
 
  • #5
hhhmortal said:
Does this mean V between the plates must stay constant at all times hence the charges increase and thus amount of energy that the capacitor stores increases?

i] If you use the same battery (so the voltage, V stays the same) to charge two capacitors, identical except for the dielectric, then the amount of charge changes, and so does the energy stored

ii] but if you disconnect the battery, with the capacitor charged, and move a dielectric in between the plates, then obviously the charge stays the same, and the potential difference (the voltage) changes … since that also changes the energy, I assume you have to do some work to force the dielectric in there! :smile:
 

What is energy stored in a capacitor?

The energy stored in a capacitor is the amount of electric potential energy that can be stored in the electric field between the capacitor's plates when it is charged.

How does energy stored in a capacitor work?

When a capacitor is charged, it creates an electric field between its plates. This field stores energy in the form of electric potential energy. The amount of energy stored depends on the capacitance of the capacitor and the voltage applied.

What is the formula for calculating energy stored in a capacitor?

The formula for calculating energy stored in a capacitor is E = 1/2 * C * V^2, where E is the energy in joules, C is the capacitance in farads, and V is the voltage in volts.

How is energy stored in a capacitor released?

Energy stored in a capacitor is released when the capacitor is discharged. This can happen when the circuit is closed or when the voltage source is removed. The energy is released in the form of an electric current.

What are some practical applications of energy stored in a capacitor?

Energy stored in a capacitor has many practical applications, such as in electronic circuits to store and release energy, in camera flashes to provide a quick burst of light, and in defibrillators to deliver a high-voltage shock to restart a person's heart.

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