# What is the Final Potential Across the First Capacitor After Switch Closure?

• phantom85
In summary, a charged capacitor is initially connected to a potential source and then removed and connected to an initially uncharged capacitor. The final potential across the first capacitor long after the switch is closed can be determined by using the equation Q=Cε and conservation of charge, resulting in a final potential of V=(C1ε)/(C1+C2). This is because both capacitors become equipotential surfaces.
phantom85
A first capacitor is initially connected to potential source ?. The charged capacitor is then removed
from the source and connected to a second initially uncharged capacitor. Determine the final potential
across the first capacitor long after the switch is closed.

## Homework Statement

Q1 charged by capacitor C1

Q=Cε

## The Attempt at a Solution

You're going to have to give some effort to the problem. What do you think is going to happen once the the switch is closed, in terms of changes in charges and potentials, since those are the only quantities that can vary?

So if it let charges at C1 when connected to voltage source to be Q' then after let charges at C1 and C2 to be Q1 and Q2. It should be Q1+Q2=Q' ?

Yes, from conservation of charge. If you use the equation you listed, you can substitute capacitance times potential for each charge, and then that should open up the potential on C1

So V(C1+C2)=C1ε , and solving for V=(C1ε)/(C1+C2) is this correct?

Yes, that's right. V is the same across both capacitors because they become equipotential surfaces.

1 person
Alright Thank you.

## 1. What is potential across capacitance?

Potential across capacitance refers to the voltage difference between the two plates of a capacitor. This potential difference is created by storing electrical charge on the plates.

## 2. How is potential across capacitance calculated?

The potential across capacitance can be calculated using the formula V = Q/C, where V is the potential difference, Q is the charge stored on the capacitor, and C is the capacitance of the capacitor.

## 3. What is the unit of potential across capacitance?

The unit of potential across capacitance is volts (V).

## 4. How does potential across capacitance affect the behavior of capacitors?

The potential across capacitance determines the amount of charge that can be stored on a capacitor, as well as the strength of the electric field between the plates. This in turn affects the capacitance and charging/discharging behavior of the capacitor.

## 5. Can the potential across capacitance be changed?

Yes, the potential across capacitance can be changed by altering the amount of charge stored on the plates or by changing the capacitance of the capacitor. This can be achieved through various methods such as varying the voltage or using different materials for the capacitor plates.

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