What is the maximum charge that can be put on a charged aluminum sphere?

In summary, the conversation centered around the possibility of charging a piece of aluminum with a negative charge of 8 Coulombs using a van der graaf generator and a strong insulator. The person asking the questions was curious about the size of the aluminum, effectiveness of the generator, rate of charge depletion, and best insulator to use. However, it was determined that the air breakdown of 1 MV/m would make it impossible to achieve this charge with a sphere of any practical size.
  • #1
Frogmansailor
2
0
I am doing some conceptual design, and was hoping to be able to get some answers here before I devote too much time to this.

I would like to be able to charge a piece of aluminum so that it holds a charge (negative) of 8 Coulombs. I was hoping to achieve this with something similar to a van der graaf generator, which would charge a spherical piece of aluminum which is encased in a strong insulator so that the charge is safely contained.

So my questions are:

How big would this piece of aluminum have to be?
Would a van der graaf type generator work for this application?
How fast would this conductor bleed it's charge?
What insulator would best reduce this loss of charge?

Thanks in advance
Dave
 
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  • #2
It's not going to happen. The field at the surface of a sphere is Q/(4*pi*epsilon_0*R^2), and air breaks down at a field strength of about 1 MV/m. To put 8 Coulombs on the sphere, you'd then need a sphere of a radius of 268 m to prevent the air around it from breaking down. 8 Coulombs is a lot of charge.
 
  • #3
Well the dielectric breakdown of air being so low is the reason I want to surround it with a better insulator, so that isn't accurate.

I realize 8 C is a ton of charge, I was just hopeful I guess. What would the maximum charge that one could put on a sphere about the size of a basketball then?
 

1. How do you create a charged object?

To create a charged object, you can use a process called "charging by friction" where you rub two materials together, such as a cloth and a plastic rod. This transfers electrons from one material to the other, creating a charge imbalance and resulting in a charged object.

2. What materials can be used to create a charged object?

Any two materials with different levels of electron affinity can be used to create a charged object through friction. Some commonly used materials include cloth and plastic, glass and silk, or rubber and fur.

3. How can you tell if an object is charged?

One way to tell if an object is charged is by using an electroscope, which is a device that can detect the presence and magnitude of an electric charge. Another method is to observe if the object is attracting or repelling other charged objects.

4. Can you create a charged object without friction?

Yes, there are other methods of creating a charged object without friction. For example, you can use a process called "charging by contact" where a charged object is brought into contact with a neutral object, transferring some of its charge to the neutral object.

5. How does creating a charged object relate to electricity?

Creating a charged object is a fundamental step in understanding electricity. It demonstrates the concept of charge transfer and how charged objects can interact with each other, leading to the flow of electricity. Many everyday objects, such as batteries, rely on creating charged objects to function.

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