Van de Graaff Problem: Solve for Electric Field Strength

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In summary, the conversation discusses using a van de Graaff generator to put negative charge on a metal sphere with a radius of 6.9 cm and a charge of -1.0×10-8 C. The question asked is to determine the electric field strength at a point 1.0 cm from the surface of the sphere using the equation E = F/q. The solution involves using a test charge and finding the force on it, then using the equation F = kq'q/r^2 to find the field E at this point. The final step is to add the radii of the sphere and the distance from the surface to get the total distance (r) for the calculation.
  • #1
Ryo124
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A van de Graaff generator puts negative charge on a metal sphere.

Suppose the radius of the sphere is a = 6.9 cm, and the charge on the sphere is Q = -1.0×10-8 C. Determine the electric field strength at a point 1.0 cm from the surface of the sphere (outside the sphere). I've done this problem over and over and am not getting the correct answer.
I've used E = F/q and made F = kq/r^2
...from there, I don't know what to do. Please help. Thanks
 
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  • #2
I think they are aking you to use a test charge (like an electron) and find the force on it at r (F = kq'q/r^2). Then find the field E at this point.
 
  • #3
step-by-step please

OK, but I am still unsure what to do.. Do you add .069m and .01m for r?? Can someone "walk" me through this step-by-step PLEASE.
 
  • #4
The field outside the sphere is the same as thought the entire charge were concentrated at a point at its center. So r would be 0.069 + 0.01.
 
  • #5
Got it. Thanks.
 

1. What is a Van de Graaff generator?

A Van de Graaff generator is a device that is used to create static electricity by accumulating electric charge on a large metal sphere. It operates by using a moving belt to transfer electric charge from a high-voltage power source to the sphere, creating a large potential difference between the sphere and its surroundings.

2. What is the "Van de Graaff problem"?

The "Van de Graaff problem" refers to a common physics problem that involves calculating the electric field strength at a point near a Van de Graaff generator. This problem is often used to demonstrate the principles of electric fields and Coulomb's law.

3. How do you solve for electric field strength in the Van de Graaff problem?

To solve for electric field strength in the Van de Graaff problem, you will need to use Coulomb's law, which states that the electric field strength at a point is equal to the electric force between two charges divided by the distance between them squared. You will also need to know the charge on the Van de Graaff generator and the distance between the point and the generator.

4. What are some common challenges when solving the Van de Graaff problem?

One common challenge when solving the Van de Graaff problem is determining the correct sign of the charges involved. It is important to remember that like charges repel each other, while opposite charges attract. Another challenge can be converting between different units of measurement, such as converting meters to centimeters or Coulombs to microCoulombs.

5. How is the Van de Graaff problem relevant to real-world applications?

The Van de Graaff problem is relevant to real-world applications because it helps us understand the principles of electric fields and the behavior of electric charges. These principles are important in a variety of fields, including electrical engineering, physics, and telecommunications. Additionally, Van de Graaff generators are used in research and medical facilities to generate high voltages for various experiments and procedures.

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