# Negative potential energy and capacitors

• Andrew Wright
In summary, the conversation discusses the concept of gravitational potential energy and its relation to negative energy in a parallel plate capacitor. It also explores the idea of zero being a special number in both gravitational potential and electric circuits. The conversation concludes by discussing the ways in which energy can be taken out of a capacitor.
potential energy is defined up to an additional constant by the way

Say parallel opposite charges plates whose distance d are:

1. infinite
2. finite ##d_0##
3. 0 and all electrons and positive ions on the plate reunite after releasing energy with short circuit.

Then energy of the states are
$$E_3<E_2<E_1$$

If we take ##E_1=0## as you do for gravity, ##E_2## is negative.

If we take ##E_3=0## as usually we do in electric circuit studies, ##E_2## is positive.
Even in gravity study, we have learned that a object of mass m in height h has potential energy ##mgh >0##.

We can take energy out of a capacitor by:

1. Letting the positive charges move further apart. That decreases the positive energy of one plate.
2. Letting the negative charges move further apart. That decreases the positive energy of one plate.
3. Letting the opposite charges get closer together. That increases the negative energy of the capacitor.
4. Draining the capacitor, which involves all those three things above.In the link in post #1, there it is mentioned something about zero being a special number among numbers, and gravitational potential at infinity being a special gravitational potential among gravitational potentials. Well, I agree with that part of the answer. (Actually only zero being an important number was mentioned. Well, it's not a very good answer IMO)

Last edited:

## 1. What is negative potential energy?

Negative potential energy is a measure of the amount of energy an object has due to its position or configuration in a system. In the case of negative potential energy, the object is in a lower energy state than its surroundings.

## 2. How is negative potential energy related to capacitors?

Negative potential energy is closely related to capacitors because capacitors store energy in the form of electric potential energy. When a capacitor is fully charged, it has a negative potential energy, as the positive and negative charges on the plates are attracted to each other and have a lower energy state.

## 3. Can capacitors have positive potential energy?

Yes, capacitors can have positive potential energy if they are not fully charged. In this case, the positive and negative charges on the plates are not fully attracted to each other, and the capacitor has a higher energy state.

## 4. How does the size of a capacitor affect its negative potential energy?

The size of a capacitor, specifically the distance between the plates, directly affects its negative potential energy. A larger distance between the plates results in a higher negative potential energy, as the charges have to overcome a larger distance to reach each other.

## 5. How is negative potential energy used in capacitors?

Negative potential energy is used in capacitors to store electrical energy. When a capacitor is connected to a circuit, it can release this stored energy in the form of an electric current. This makes capacitors useful in a variety of electronic devices, such as cameras, computers, and flashlights.

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