# Capacitors, Entropy & Energy Loss

• RobinSky
In summary, the conversation discusses the concept of entropy and its relation to energy loss in a system. It is mentioned that while an increase in entropy is a natural process, the loss of energy in a capacitor is mainly due to electromagnetic forces. The role of resistance in dissipating energy and increasing entropy is also discussed. It is noted that entropy is a description, not a cause, of energy loss. The example of a capacitor and light bulb is used to illustrate this concept. The conversation ends with a clarification that entropy increase happens in the resistor, not the capacitor, and that the energy will eventually be converted into heat, leading to an increase in entropy.
RobinSky
I was thinking of this following example:

Consider you charge a capacitor to its max with a battery, now replace the battery with a light bulb for example. The capacitor is starting to lose all the energy it had stored, is this a result due to entropy?
I mean I've learned that an increase in entropy is a natural process, and for me, when the capacitor is losing it's energy, the system gets an increase in entropy, right? Same goes with common batteries, leave them to be (whether in use or not), and after enough time they are not usable anymore. So is it okay to see this as a result due to entropy?

Regards, Robin.

None? :/

Entropy is defined as kln(Ω) where k is Boltzmann's constant, ln() is the natural logarithm function, and Ω is the number of different ways that a system can have particular values of whatever properties one is concerned with (i.e., the ones you are measuring).

While I imagine that the thermodynamic tendency to increase entropy could contribute the current produced when the battery is replaced, I would think that the electromagnetic forces involved would dominate under ordinary circumstances. That is, the attraction of opposite charges (the opposing surfaces in a capacitor are oppositely charged) is the main cause of the motion of the electrons.

RobinSky said:
I was thinking of this following example:

Consider you charge a capacitor to its max with a battery, now replace the battery with a light bulb for example. The capacitor is starting to lose all the energy it had stored, is this a result due to entropy?

The energy given off by the capacitor is not identical to the actual loss of energy. The actual loss of energy depends on how much energy was dissipated as resistance. Part of the resistance can be in the capacitor, and the most of the rest is dissipated in other parts of the circuit.

RobinSky said:
I mean I've learned that an increase in entropy is a natural process, and for me, when the capacitor is losing it's energy, the system gets an increase in entropy, right?

The entropy is based on energy losses that lead to a temperature change in the system. A positive change in entropy means a loss of energy and a drop of temperature for a system. You also have an energy increase and temperature rise for another system. It's the cooling process for one system and the heating process for another, that determines the entropy.

RobinSky said:
Same goes with common batteries, leave them to be (whether in use or not), and after enough time they are not usable anymore. So is it okay to see this as a result due to entropy?

Regards, Robin.

Entropy is the result of that, not the cause of that. Entropy is a description - not a mechanism.

It's a very good question. Thanks, I learned a lot.

Thanks for the replies guys! I say, as the person above, I learned a lot! There might be a few more follow-up questions from me the comin' days though!

Entropy increase happens in the resistor (light bulb in this case), not in capacitor. If you connect inductor instead, you will get an LC-tank. The energy will oscillate back and forth between inductor and capacitor. Ideal LC tank would oscillate indefinitely and the entropy would stay the same. In the real world oscillations will eventually die out and the energy will be converted into heat (with corresponding increase in entropy) due to the resistance of the wires including those in the inductor and capacitor.

Ah! That was a good "analogy", thanks again for a good answer.

## 1. What is a capacitor?

A capacitor is an electronic component that stores electrical energy in an electric field. It consists of two conductive plates separated by an insulating material, usually a dielectric. When a voltage is applied, one plate becomes positively charged and the other becomes negatively charged, creating an electric field between them.

## 2. How does a capacitor work?

A capacitor works by storing energy in the form of an electric field. When a voltage is applied, electrons from the negative plate are attracted to the positive plate, creating an electric field. The capacitor can then release this stored energy when needed, such as in an electronic circuit.

## 3. What is entropy in relation to capacitors?

Entropy is a measure of the disorder or randomness in a system. In the context of capacitors, entropy can refer to the amount of disorder in the electric field between the plates. As the capacitor discharges, the electric field becomes more disordered, resulting in an increase in entropy.

## 4. How does energy loss occur in capacitors?

Energy loss in capacitors can occur through various mechanisms, including leakage current, dielectric losses, and parasitic resistance. These losses can result in a decrease in the amount of stored energy and can also affect the performance of the capacitor in an electronic circuit.

## 5. How can energy loss in capacitors be minimized?

To minimize energy loss in capacitors, it is important to choose the right type and quality of capacitor for a specific application. This includes selecting a capacitor with a suitable dielectric material, as well as considering factors such as temperature and frequency. Proper circuit design and maintenance can also help reduce energy loss in capacitors.

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