Electrostatic voltage and current

In summary: So the VdG sphere may reach a max voltage wrt the ground (we can now read that all voltages wrt the ground unless otherwise specified).
  • #1
abdo799
169
4
If we had a van de graaff generator, near the sphere there is a metal plate ( not touching) and it's wired to the ground (a resistor is connected to the wire) , as the voltage on the surface of the sphere increases, the voltage at the plate does too, creating a potential difference between the plate and the ground and a current will flow, will this current depend on the resistance of the wire? ( no electrical discharges occurs )
 
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  • #2
Yes - the current through any resistor depends on the potential difference across it and it's resistance.
A wire is another resistor - usually with a very small value of resistance.
If you have an ammeter in there, this will also affect the current.

Note: you are not describing a static situation.
 
  • #3
But when the voltage reaches its maximum the current will stop, right??
 
  • #4
Voltage where?
 
  • #5
There is a potential at the surface of the sphere, as we increase the distance ( from the center of the sphere) increases in radial direction the potential decreases, but the potential reaches a maximum after that the generator can't build up more charge
 
Last edited:
  • #6
If the case i am describing is not clear, i can draw a sketch and upload if you want
 
  • #7
Oh OK - some notes:
A single location cannot have a voltage by itself - you'll notice you need two leads to make a voltmeter work right?
So the VdG ("Van der Graaf" - saves typing) sphere may reach a max voltage wrt the ground (we can now read that all voltages wrt the ground unless otherwise specified ... I needed to be sure).

You are using the sphere to induce a voltage on a plate, and the plate is connected to the ground by a wire.

In a secondary school level model:
What happens is that the sphere separates charges in the plate - repelling like charge and attracting the opposite.
This means that charges move about the plate until the electric field due to the charge separation is equal and opposite the electric field due to the VdG sphere. That's a current, but it does not last long.

Basically you end up with like charges on the opposite side of the plate to the VdG.

Attach a wire from the opposite side to the ground and charges from the ground can travel up the wire to cancel the charges on the far side of the plate. You can think of the ground as a large source for any charges that may be attracted or a sink for a any charges that may be repelled. Note though: this is a very qualitative description. The process is called "charging by induction" - you may have heard of it already?

Re your question then:
But when the voltage reaches its maximum the current will stop, right??
... no. As you saw from the above, the voltage on the VdG sphere can be at it's maximum and there is still a current. The current flows as long as there are charges available to flow.
 
  • #8
Okay, thanks
 

Related to Electrostatic voltage and current

1. What is electrostatic voltage?

Electrostatic voltage is a measure of the electric potential difference between two points in an electric field. It is also known as electric potential or voltage difference.

2. How is electrostatic voltage different from electric current?

Electrostatic voltage is a measure of the potential difference between two points, while electric current is a measure of the flow of electric charge between those two points. Voltage is measured in volts (V) and current is measured in amperes (A).

3. What causes electrostatic voltage?

Electrostatic voltage is caused by the separation of positive and negative charges in an electric field. This separation creates a potential difference between the two points, which can result in the flow of electric current.

4. How is electrostatic voltage measured?

Electrostatic voltage can be measured using a voltmeter, which is a device that measures the potential difference between two points. It can also be calculated using the formula V=IR, where V is voltage, I is current, and R is resistance.

5. What are some practical applications of electrostatic voltage and current?

Electrostatic voltage and current are used in a variety of everyday devices such as batteries, power outlets, and electronic devices. They are also important in industrial processes such as electroplating and electrostatic painting. In addition, electrostatic voltage is used in medical equipment such as defibrillators and electrocardiograms.

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