Finding potential difference across capacitor plates?

In summary: Then solve for the potential difference across the plates of the capacitor filled with a dielectric. The potential difference across the plates of the capacitor filled with a dielectric is equal to the amount of electrical energy that would be stored in the capacitor if it were empty.
  • #1
cheap_noob
3
0

Homework Statement


Two capacitors are identical, except that one is empty and the other is filled with a dielectric (k=3.6). The empty capacitor is connected to a -11V battery. What must be the potential difference across the plates of the capacitor filled with a dielectric so that it stores the same amount of electrical energy as the empty capacity?


Homework Equations


C=q/V C=kε°0)A/d E=q/(ε°)A
Estored=1/2qv = 1/2 cv^2


The Attempt at a Solution


I don't really know what to do. I'm guessing that there's a lack of information but however the part about the empty capacitor, that would mean Estored = 0 right? But even though I plug in something with zero and solve for C, C would be zero which would mean 0=q/V or the other equation and if I solve for a variable it would be just zero.

I'm guessing my logic is probably wrong but I'm really lost. I basically have only 2 known variables from the question.
Any help would be awesome!
 
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  • #2
Empty capacitor means that the space between the plates is not filled with dielectric.

ehild
 
  • #3
So does that mean I let C=kε°A/d equal to each other so kε°A/d=kε°A/d?
And then from that plug in 3.6 for one of the k, and 1 for the other?
And from that, the k's will cancel, the A's will cancel b/c identical, and I'm not sure about the d's. Well is that the right method or am I still doing something wrong?
 
  • #4
cheap_noob said:
So does that mean I let C=kε°A/d equal to each other so kε°A/d=kε°A/d?
And then from that plug in 3.6 for one of the k, and 1 for the other?
And from that, the k's will cancel, the A's will cancel b/c identical, and I'm not sure about the d's. Well is that the right method or am I still doing something wrong?

How would the k's cancel if they are not the same?
 
  • #5
gneill said:
How would the k's cancel if they are not the same?

Oops sorry. Well I meant that there will be a ratio when you divide one by the other; when transferring k over to solve for the unknown variable, there will be an actual number
Anyways I'm still lost
 
  • #6
cheap_noob said:
Oops sorry. Well I meant that there will be a ratio when you divide one by the other; when transferring k over to solve for the unknown variable, there will be an actual number
Anyways I'm still lost

Start by working out how the values of the two capacitors are related (write an expression).
 

1. What is potential difference across capacitor plates?

Potential difference across capacitor plates refers to the difference in electric potential between the positive and negative plates of a capacitor. It is measured in volts and represents the amount of work required to move a unit of charge from one plate to the other.

2. How is potential difference across capacitor plates calculated?

The potential difference across capacitor plates can be calculated by dividing the charge on the plates by the capacitance of the capacitor. It can also be calculated by multiplying the electric field strength between the plates by the distance between the plates.

3. How does the potential difference across capacitor plates affect the energy stored in the capacitor?

The potential difference across capacitor plates directly affects the energy stored in the capacitor. As the potential difference increases, the energy stored also increases. This is because the potential difference is directly proportional to the charge and capacitance, which are both factors in the energy formula (E=1/2CV^2).

4. What factors can affect the potential difference across capacitor plates?

The potential difference across capacitor plates can be affected by the capacitance of the capacitor, the distance between the plates, and the amount of charge on the plates. It can also be affected by the material and dielectric used in the capacitor, as well as the voltage applied to the circuit.

5. How does the potential difference across capacitor plates change over time?

The potential difference across capacitor plates can change over time in a number of ways. It can decrease as the capacitor discharges, or it can increase as the capacitor charges. It can also fluctuate in an alternating current circuit, or remain constant in a direct current circuit.

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