Something about parallel capacitors

In summary: Yes, I do pay attention. :)In summary, according to the textbook, if the distance between the parallel plates is increased before opening the switch, the dielectric constant is constant. If the distance is increased after the switch is opened, the dielectric constant decreases and the capacitance and voltage between the plates increase.
  • #1
illuminati23
2
0
If two parallel plates are facing one another and one of them are moved without opening the switch, what's the difference with moving the plates after opening the switch?
 
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  • #2
Sorry, You'll have to be more detailed than that.
 
  • #3
If they are moved before opening, V is constant. If after, Q is constant.
 
  • #4
willem2 said:
Sorry, You'll have to be more detailed than that.

So my textbook says that if the distance between the parallel plates are increased from d to d' without opening the switch first(so that means that electric current is flowing), then only V is constant and Q, E is not constant. But if d is increased to d' after opening the switch(stopping the current), then Q and E is constant.
 
  • #5
Moving the plates involves doing work. That work will be transferred to potential energy or Kinetic Energy (a flow of charge), depending on whether there is a conducting path or not.
 
  • #6
illuminati23 said:
So my textbook says that if the distance between the parallel plates are increased from d to d' without opening the switch first(so that means that electric current is flowing), then only V is constant and Q, E is not constant. But if d is increased to d' after opening the switch(stopping the current), then Q and E is constant.
When the switch is closed then V is the value of the power supply. So if you then increase d you put some energy back in the power supply. Increasing d means lowering the value of the capacitor. Since Q=C*V then Q will decrease. Also since E=V/d it means that E decreases. So your text reads: only V is constant, and Q and E are not constant. I think your book is a bit confusing (but correct).
The second part is OK.
 
  • #7
illuminati23 said:
If two parallel plates are facing one another and one of them are moved without opening the switch, what's the difference with moving the plates after opening the switch?

-dielectric constant will decrease, capacitance will decrease, voltage between the plates will increase, and some of the charges will move back to the power supply. The energy to move the electrons back to the source will come from the work of the force that is used to depart the plates.
 
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  • #8
crx said:
-dielectric constant will decrease, capacitance will decrease, voltage between the plates will increase, and some of the charges will move back to the power supply. The energy to move the electrons back to the source will come from the work of the force that is used to depart the plates.

Dielectric constant is a material property, it would not change here unless one were to change the dielectric between the plates.
 
  • #9
Born2bwire said:
Dielectric constant is a material property, it would not change here unless one were to change the dielectric between the plates.

Of course it doesn't! I just wanted to see if you pay attention...:redface:
 
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1. What are parallel capacitors?

Parallel capacitors are two or more capacitors connected side by side with each other, sharing the same voltage source. They are also known as parallel plate capacitors.

2. How are parallel capacitors different from series capacitors?

Parallel capacitors have the same voltage across each capacitor, while series capacitors have the same charge across each capacitor. Additionally, in parallel capacitors, the total capacitance is equal to the sum of individual capacitances, while in series capacitors, the total capacitance is less than the capacitance of each individual capacitor.

3. What is the formula for calculating the total capacitance of parallel capacitors?

The formula for calculating the total capacitance of parallel capacitors is: Ctotal = C1 + C2 + C3 + ..., where C1, C2, C3, etc. are the individual capacitances of each capacitor.

4. What happens to the total capacitance when adding more capacitors in parallel?

The total capacitance increases when more capacitors are added in parallel. This is because the plates of the capacitors are connected side by side, increasing the effective area of the plates and therefore increasing the total capacitance.

5. What are some real-life applications of parallel capacitors?

Parallel capacitors are used in various electronic devices such as computers, televisions, and radios. They are also commonly used in power factor correction circuits, where they help improve the efficiency of electrical systems by reducing the amount of reactive power drawn from the power source.

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