Capacitor how the plates are connected

In summary, the potential difference between the plates of capacitor C1 is 20V, while capacitor C2 has a potential difference of 4V. When the plates carrying opposite charges are connected, the potential difference decreases to 2V. Using the equation Q=C/V, it can be determined that the final charge is equal to the initial charges of both capacitors, and the value of C1 can be found using the equation Q1 - Q2 = C1*V.
  • #1
rasmusuperfan
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Homework Statement


Capacitor C1 is charged so that potential difference between its plates is 20V. Another capacitor C2=33 microF has potential difference of 4 V. After plates of the capacitor that carry the charge of the opposite sign were connected the potential difference became 2V, find C1.


Homework Equations


Q=C/V


The Attempt at a Solution


I know Q1=C1*20V and Q2=(33uF)*(4V), but don't have the slightest clue what happens when the plates are connected. Are they connected in series, or parallel, does that even matter? I know there is a conservation of charges, but would it be something like (Q1-Q2) = Ceq*V? Thanks for any help or guidance
 
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  • #2


They end up in parallel, and yes, there will be some charge cancellation.
 
  • #3


I am sorry, but I still don't see what to do. I feel like this is a simple problem, but I am lost. I don't want to seem like I am just asking for an answer, but I've been struggling with this for the past 2 hours and nothing is making sense. After they are connected it would be something like Q=(C1+C2)*V, but what is the charge? Would Q= Q1-Q2 or something like that?
 
  • #4


Yes, Q1 - Q2, or Q2 - Q1, whichever yields a positive remainder -- it is stated that the final potential difference is 2V, a positive number.
 
  • #5
!


When the plates of the two capacitors are connected, they are essentially connected in parallel. This means that the potential difference across both capacitors is the same, and the total charge on the two capacitors is equal. Using the equation Q=C/V, we can set up the following equation:
(Q1 + Q2) = Ceq * 2V
Since we know the values of Q1 and Q2, we can substitute them in and solve for Ceq:
(20C1 + 33uF * 4V) = Ceq * 2V
Ceq = (20C1 + 132uF)/2V
Since the potential difference across C1 is 20V, we can also use the equation Q=C1*V to find the value of Q1:
Q1 = C1 * 20V
Substituting this into our first equation, we get:
(C1 * 20V + Q2) = Ceq * 2V
Solving for C1, we get:
C1 = (Ceq * 2V - Q2)/20V
Substituting in the value of Ceq, we get:
C1 = ((20C1 + 132uF)/2V * 2V - 33uF * 4V)/20V
Simplifying, we get:
C1 = (20C1 + 132uF - 132uF)/20V
C1 = 20C1/20V
C1 = Ceq
Therefore, the value of C1 is equal to the equivalent capacitance of the two capacitors when connected in parallel.
 

1. How are the plates in a capacitor connected?

The plates in a capacitor are connected through a dielectric material, which is an insulating material placed between the plates to prevent direct contact. The plates are usually made of conductive materials such as metal and are connected to the circuit through wires or other conductive materials.

2. What is the purpose of connecting the plates in a capacitor?

The purpose of connecting the plates in a capacitor is to store electric charge. When a voltage is applied to the capacitor, one plate becomes positively charged and the other becomes negatively charged. This creates an electric field between the plates, which stores the charge. The capacitor can then release this stored charge when needed in a circuit.

3. What happens if the plates in a capacitor are not connected properly?

If the plates in a capacitor are not connected properly, it can lead to a malfunction in the circuit. For example, if the plates are not connected to the circuit, the capacitor will not be able to store or release charge, rendering it useless. If the plates are connected incorrectly, it can cause a short circuit and potentially damage the capacitor or other components in the circuit.

4. How are the plates connected in different types of capacitors?

The way the plates are connected in a capacitor depends on its type. In a parallel plate capacitor, the plates are connected in parallel, meaning they are aligned next to each other. In a cylindrical or spherical capacitor, the plates are connected in series, meaning they are stacked on top of each other. In a variable capacitor, the plates can be moved closer or farther apart to change the capacitance.

5. Is there a specific way to connect the plates in a capacitor?

Yes, there is a specific way to connect the plates in a capacitor. The positive plate should be connected to the positive terminal of the circuit, and the negative plate should be connected to the negative terminal. This ensures that the capacitor is properly charged and discharged when necessary. Additionally, the plates should be connected securely to prevent any loose connections that could cause issues in the circuit.

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