How can a conductive surface be held at a desired potential?

[BucketOfFish]

I was reviewing some things relating to electric fields around conducting surfaces, and the book I was using (Purcell) mentioned that a conducting surface can be held at any arbitrary electric potential (within reason). My question is, how would this actually be done in practice? Purcell mentioned something about using a battery, but my circuitry intuition is weak, so I don't see how this can establish a desired potential starting from a neutral surface.

 

[gadong]

For example, attach the positive end of an 8 V battery to the metallic surface, and Earth the negative end. Now all parts of your surface are "floating" at a potential of +8 V relative to earth.

Batteries in series are good to use for this purpose because they provide a stable ripple-free potential. For high voltages you'd have to use a power supply similarly connected to the surface and to earth.

Edit: A variable resistor can be used to generate a particular potential.

 

[BucketOfFish]

Please excuse my ignorance, but I'm not sure how a battery works. If each end is connected to a conductive surface (without completing the circuit), will electrons flow through the battery until the two surfaces reach the correct potential difference? Also, what is driving the electrons? I realize it's some kind of chemical reaction in the battery, but doesn't the circuit need to be complete for the battery to provide work?

 

[gadong]

There will be a momentary flow of electrons (too rapid and too small to detect using conventional means), but this will stop once the potential has been established. The set-up described is not a circuit and can't be analysed using conventional electronics ideas.

 

[PJC01]

I can provide a response to your question about how a conductive surface can be held at a desired potential. The key concept here is the use of a battery, which is a device that can store and provide electrical energy.

To understand how a battery can hold a conductive surface at a desired potential, let's first review the basics of electric potential. Electric potential is a measure of the potential energy per unit charge at a certain point in an electric field. In simple terms, it is a measure of how much work is required to move a unit of charge from one point to another in an electric field.

Now, let's imagine a conducting surface that is initially neutral, meaning that it has an equal number of positive and negative charges. If we want to hold this surface at a desired potential, we need to introduce an electric field that will push the positive and negative charges in opposite directions, creating a separation of charges on the surface. This separation of charges will create an electric potential difference between two points on the surface, and the magnitude of this potential difference will depend on the strength of the electric field.

This is where the battery comes in. By connecting the battery to the conducting surface, we can create an electric field that will push the charges in the desired direction and establish the desired potential on the surface. The battery acts as a source of electric potential, providing the necessary energy to create the electric field.

The exact circuitry required to hold a conductive surface at a desired potential will depend on the specific setup and materials being used. However, the basic principle remains the same – by using a battery or other source of electric potential, we can create an electric field that will hold a conductive surface at a desired potential.

I hope this explanation helps to clarify how a conductive surface can be held at a desired potential. As a scientist, it is important to have a strong understanding of the fundamentals of electric fields and potential in order to design and conduct experiments involving conducting surfaces.