1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Capacitors: Series Capacitance Concepts

  1. May 10, 2008 #1
    1. The problem statement, all variables and given/known data
    The sketch below is a side view of two capacitors consisting of parallel plates in air. The capacitor plates are equal in area but the plate separation differs as shown. Individual capacitors are specified with two letters, for example WX is a single capacitor. The charge on plate W is represented by QW.

    (Img is here)


    2. Relevant equations
    E = (.5)*C*V^2
    Q = C*V
    C = EA/d

    3. The attempt at a solution

    A potential is applied between points A and B. For each of the statements below choose the proper response.

    Increase If capacitor WX is eliminated from the circuit, the the energy stored in capacitor ZY will....
    It will increase because the voltage drop on ZY will increase

    Increase If capacitor ZY is eliminated from the circuit, the magnitude of QX will....
    Increase, voltage drop will increase

    Stay the Same If the plate separation for capacitor WX increases, the energy stored in capacitor ZY will ....
    The capacitance of ZY doesn't change

    Less Than The potential difference across capacitor WX is ______ the potential difference across capacitor ZY.
    Wx has a larger distance

    Equal to QX + QZ is _____ zero.
    All charges in a series capacitor are the same.

    Less than The energy stored in capacitor WX is ______ the energy stored in capacitor ZY.
    Because there is less voltage

    Equal to The electric field between plates Z and Y is ______ the electric field between plates W and X.
    Electric field is proportional to charge

    I know I'm wrong. What am I doing wrong?
     
  2. jcsd
  3. May 10, 2008 #2
    Let me try again...

    1. The problem statement, all variables and given/known data
    The sketch below is a side view of two capacitors consisting of parallel plates in air. The capacitor plates are equal in area but the plate separation differs as shown. Individual capacitors are specified with two letters, for example WX is a single capacitor. The charge on plate W is represented by QW.

    (Img is here)

    2. Relevant equations
    E = (.5)*C*V^2
    Q = C*V
    C = EA/d

    3. The attempt at a solution

    A potential is applied between points A and B. For each of the statements below choose the proper response.

    If capacitor WX is eliminated from the circuit, the the energy stored in capacitor ZY will increase.
    It will increase because the voltage drop on ZY will increase

    If capacitor ZY is eliminated from the circuit, the magnitude of QX will increase.
    Increase, voltage drop will increase

    If the plate separation for capacitor WX increases, the energy stored in capacitor ZY will stay the same.
    The capacitance of ZY doesn't change

    The potential difference across capacitor WX is less than the potential difference across capacitor ZY.
    Wx has a larger distance

    QX + QZ is equal to zero.
    All charges in a series capacitor are the same.

    The energy stored in capacitor WX is less than the energy stored in capacitor ZY.
    Because there is less voltage

    The Electric Field between plates Z and Y is equal to the electric field between plates W and X.
    Electric field is proportional to charge

    I know I'm wrong.

    WHAT AM I DOING WRONG?

    --yuvlevental
     
  4. May 10, 2008 #3
    i need help

    really, i do
     
  5. May 10, 2008 #4
    im not joking
     
  6. May 10, 2008 #5
    ill keep posting until someone answers
     
  7. May 10, 2008 #6
    pleaaaaaaaaaaaaaaseeeeeeeeeeeeeeeeeeeeeee answer
     
  8. May 10, 2008 #7

    alphysicist

    User Avatar
    Homework Helper

    Hi yuvlevental,

    Here are a few problems I see:

    The capacitance of ZY doesn't change, but the voltage across ZY depends on the capacitance of WX.

    What is the relationship between plate separation and potential difference?

    Why do you say there is less voltage? What is the relationship between voltage and capacitance?

    Your reasoning gives you the right answer herem but the reasoning itself is not quite right. The electric field between the capacitors is proportional to the charge density (charge/area). For example, if in this problem one capacitor had twice the area of the other, but still the same charge, its field would be half.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Capacitors: Series Capacitance Concepts
Loading...