Capacitor Analogy: Exploring William J Beaty's Water Analogy

In summary, the conversation discusses a website by William J Beaty that explains the functioning of capacitors using a water analogy. The question is whether a parallel can be drawn between the analogy and introducing a dielectric with a dielectric constant k. The response is that the analogy can be applied, as the rigidity of the rubber plate in the analogy represents capacitance, and introducing a dielectric is like changing the thickness of the rubber plate. However, the article is considered slightly inaccurate as it does not mention the textbook definition of capacitors having no net charge change, but does acknowledge that each plate does experience a net charge gain.
  • #1
i.mehrzad
84
0
I have read this site by William J Beaty http://amasci.com/emotor/cap1.html
It lucidly explains the functioning of the capacitor with a water analogy.
I have a question with respect to this.
If in a capacitor we introduce a dielectric with dielectric constant k then can a parellel be drawn with respect to this analogy.
 
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  • #2
Yes. You could say that in the analogy, the rigidity of the rubber plate accounts for the capacity: a thicker plate (more rigid) means less capacity and a thinner more capacity. The introducing a dielectric is the same as changing thick rubber plate for a thinner one.
 
  • #3
Capacitance

That article is a little iffy. It's not wrong, but neither is the textbook definition. Of course capacitors have no net charge change. This can be seen simply from the sign convention that one plate has charge +Q and the other has charge -Q.

However, each plate does experience a net charge gain, which can be seen simply by separating a charged capacitor and using a single plate to induce a current flowing to a ground.
 

1. What is a capacitor?

A capacitor is an electronic component that stores electrical energy by accumulating an electrical charge on two conductive plates separated by an insulating material. It is commonly used in electronic circuits to regulate voltage, filter out noise, and store energy.

2. What is the water analogy used by William J Beaty to explain capacitors?

The water analogy compares the flow of water through pipes to the flow of electricity through a capacitor. In this analogy, the pipes represent the conductive plates of the capacitor, the water represents the electrical charge, and the pump represents the power source. Just as a capacitor can store electrical charge, a pipe can store water when a pump is used to push it in.

3. How does the water analogy explain the capacitance of a capacitor?

The capacitance of a capacitor is determined by the surface area of the conductive plates and the distance between them. In the water analogy, this would be represented by the size of the pipes and the length between them. A wider pipe or shorter distance allows for more water to be stored, just as a larger surface area or shorter distance between plates allows for a higher capacitance.

4. Can the water analogy be used to understand the charging and discharging of a capacitor?

Yes, the water analogy can be used to explain the charging and discharging of a capacitor. When the pump is turned on, water flows into the pipes, representing the capacitor charging. When the pump is turned off, the water stops flowing, representing the capacitor discharging. The flow of water is similar to the flow of electrical charge in a capacitor.

5. How does the water analogy explain how a capacitor blocks DC but allows AC to pass through?

A capacitor blocks direct current (DC) because it cannot flow through the insulating material between the plates. However, alternating current (AC) can pass through a capacitor because it constantly changes direction, allowing the electrical charge to flow back and forth between the plates. In the water analogy, this would be similar to water being pumped back and forth between the pipes instead of flowing continuously in one direction.

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