How does a dielectric affect the capacitance of a capacitor?

In summary, the conversation discusses the concept of capacitance and how it changes when capacitors are connected in series or parallel. One person questions the answer key's solution for a specific problem, while another person provides clarification on the correct formula for equivalent capacitors. The conversation ends with a suggestion to calculate the total energy using the given quantities.
  • #1
catch22
62
0

Homework Statement


upload_2015-11-17_17-13-45.png


Homework Equations

The Attempt at a Solution


for #14, I remember a battery maintains the potential therefore, V should be constant; dielectric increases charge on plates and increases capacitance but I couldn't find an option that matched.

The answer key says "d" but I believe V should stay the same so perhaps there is a typo?
Can anyone confirm this?
 
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  • #2
Another question:

upload_2015-11-17_17-33-7.png


Could someone explain this to me? Answer key says C.
I thought in series, Ceq = C1 + C2 + C3...

and in parallel Ceq = 1/C1 + 1/C2 + 1/C3...
 
  • #3
For the first part, i agree with you that the potential difference between two plates should be the same because it is still attached to a battery. For the second question, think it this way: which quantity is the same for all the capacitors when you connect them in parallel, while which quantity is the same when you connect them in series?
 
  • #4
honlin said:
For the first part, i agree with you that the potential difference between two plates should be the same because it is still attached to a battery. For the second question, think it this way: which quantity is the same for all the capacitors when you connect them in parallel, while which quantity is the same when you connect them in series?
in series, Q is constant through out.

Parallel , V is constant through out.
 
  • #5
catch22 said:
Could someone explain this to me? Answer key says C.
I thought in series, Ceq = C1 + C2 + C3...

and in parallel Ceq = 1/C1 + 1/C2 + 1/C3...

Your formulae for the equivalent capacitors are wrong. They are not the same as in case of resistors!
 
  • #6
catch22 said:
in series, Q is constant through out.

Parallel , V is constant through out.
Yea, you can work out from there. Try to find the total energy from the Q,C,V.
 
  • #7
ehild said:
Your formulae for the equivalent capacitors are wrong. They are not the same as in case of resistors!
whoops, for Ceq = C1 + C2 + C3... in parallel

Ceq = 1/C1 + 1/C2 + 1/C3... in series
 

What is a dielectric in a capacitor?

A dielectric in a capacitor is a non-conducting material that is placed between the two conducting plates of a capacitor. It acts as an insulator and helps to increase the capacitance of the capacitor.

What is the purpose of a dielectric in a capacitor?

The purpose of a dielectric in a capacitor is to increase the capacitance by reducing the electric field between the two plates of the capacitor. This allows for a greater charge to be stored on the capacitor.

How does a dielectric affect the capacitance of a capacitor?

A dielectric increases the capacitance of a capacitor by reducing the electric field between the two plates. This allows for a greater charge to be stored on the capacitor without increasing the voltage.

What are some common materials used as dielectrics in capacitors?

Some common materials used as dielectrics in capacitors include air, ceramic, paper, mica, and plastic. The material used depends on the specific application and desired properties of the capacitor.

Can a dielectric in a capacitor ever decrease the capacitance?

Yes, a dielectric in a capacitor can decrease the capacitance if it is not a good insulator. This can happen if the material has a high dielectric constant, which allows for more charge to be stored on the plates and decreases the overall capacitance of the capacitor.

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