Equation to relate voltage to distance of a spark

In summary, the conversation discusses calculating the minimum distance for a spark to jump with a given voltage in a vacuum. The speaker is looking for a general equation and mentions not needing to consider the shape of the charged bodies. They also provide a link to a source that may be helpful.
  • #1
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I need to calculate the minimum distance for which a charge of some voltage will jump. Is there any equation that relates distance of a spark jump to voltage (a fairly generalised equation will do, I don't need to worry about strange shapes of the charged bodies that the charge leaps between or anything). Assume that this occurs in a vacuum. (This isn't homework, just part of a side project, and I am stuck because I can't figure out the above sub-problem, which hopefully isn't too difficult).
 
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  • #3


Yes, there is an equation that relates voltage to the distance of a spark jump. This equation is known as the Paschen's Law and it states that the minimum distance (d) for a spark to jump is inversely proportional to the product of the pressure (p) and the voltage (V) and directly proportional to the natural logarithm of the product of the pressure and the voltage. Mathematically, it can be expressed as:

d = a * (p * V) / ln(p * V)

where a is a constant that depends on the gas used and the shape of the electrodes.

In a vacuum, the pressure is close to zero, so the equation simplifies to:

d = a * V / ln(V)

This equation is fairly general and can be used to calculate the minimum distance for a spark to jump for different voltages in a vacuum. However, it is important to note that this equation is only valid for uniform electric fields and does not take into account the shape of the charged bodies or any other factors that may affect the spark jump distance. Therefore, it is recommended to use this equation as a starting point and make adjustments based on the specific conditions of the experiment.
 

1. What is the equation used to relate voltage to distance of a spark?

The equation used to relate voltage to distance of a spark is known as the Paschen's Law. It is represented as V = Bpd ln (A/pd +1), where V is the voltage, p is the pressure, d is the distance, B is a constant, and A is the minimum breakdown voltage.

2. How is Paschen's Law derived?

Paschen's Law is derived from the Townsend discharge equation, which describes the breakdown of a gas due to the creation of a plasma. It takes into account the effects of gas pressure and distance on the breakdown voltage.

3. What factors affect the breakdown voltage according to Paschen's Law?

The breakdown voltage according to Paschen's Law is affected by the type of gas, the pressure of the gas, the distance between the electrodes, and the shape and material of the electrodes. These factors all influence the strength of the electric field and the likelihood of a spark occurring.

4. Can Paschen's Law be applied to all types of gases?

No, Paschen's Law is only applicable to gases that exhibit Townsend discharge, which is the creation of a plasma due to the ionization of gas molecules by an electric field. This means that it cannot be applied to non-ionizing gases such as noble gases.

5. How is Paschen's Law used in practical applications?

Paschen's Law is used in practical applications such as in the design of spark plugs for internal combustion engines and in the design of gas discharge tubes for lighting. It helps engineers determine the appropriate voltage and distance needed for a spark to occur, ensuring efficient and safe operation of these devices.

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