Why doesn't capacitance decrease with increase in temperature?

[ARAVIND113122]

why doesn't capacitance decrease with increase in temperature??

It is known that conductivity increases with temperature.This is because heat provides kinetic energy to the electrons in a substance,thus increasing the rate of "flow" of electrons.Considering this,the electrons in a dielectric in a capacitor should also get excited on heating.This means the electrons are more likely to break away from one end and would travel to the other end.This means that the CAPACITY OF THE DIELECTRIC TO RESIST THE FLOW OF CHARGES[which in fact the capacitance of dielectric in the given set up] MUST DECREASE,WITH INCREASE IN TEMPERATURE.
am i right or is there something more to it??
please help me.

 

[agentas]

Energy in capacitor in stored in electric field between the plates of capacitor.By changing T you are not influencing C.Remember this

 

[ARAVIND113122]

the question is-why? what is wrong in the explanation i have given?
Wouldn't increasing temperature excite the electrons and thus,reduce the ability of the dielectric to prevent the charges from flowing?
if you look at what a capacitor really is-it is a device that helps in maintaining a potential difference without allowing the charges to flow.It is this ability that is called capacitance.A good capacitor can hold more more charges without breaking down.But if the charges are highly excited[i.e, the temperature is very high],then the capacitor cannot "hold" them.So,at different temperatures,the same set up will have different capacitance.Isn't it?

 

[davenn]

It is known that conductivity increases with temperature.This is because heat provides kinetic energy to the electrons in a substance,thus increasing the rate of "flow" of electrons.Considering this,the electrons in a dielectric in a capacitor should also get excited on heating.This means the electrons are more likely to break away from one end and would travel to the other end.This means that the CAPACITY OF THE DIELECTRIC TO RESIST THE FLOW OF CHARGES[which in fact the capacitance of dielectric in the given set up] MUST DECREASE,WITH INCREASE IN TEMPERATURE.
am i right or is there something more to it??
please help me.

you have a few bad assumptions in your reasoning. from wiki...

Temperature dependence
In general, electrical resistivity of metals increases with temperature, while the resistivity of intrinsic semiconductors decreases with increasing temperature. In both cases, electron–phonon interactions can play a key role. At high temperatures, the resistance of a metal increases linearly with temperature. As the temperature of a metal is reduced, the temperature dependence of resistivity follows a power law function of temperature.

and to add to your misunderstanding... think of superconductors research and use...

They are not hot are they ? rather they are supercooled

cheers
Dave

 

[davenn]

the question is-why? what is wrong in the explanation i have given?

because of your incorrect assumption about temperature and conductivity

see my previous comments have a read in wiki for yourself...

http://en.wikipedia.org/wiki/Electrical_resistivity_and_conductivity

cheers
Dave

 

[willem2]

If the conductivity is higher you don't get a higher capacitance, you get more leakage.
What you want it the permittivity. I looked up a capacitor data sheet, and there seems to be a maximum usually.

http://www.niccomp.com/Products/TC_Ceramics.pdf"

I think capacitance goes down for higher temperatures, because the random movement of the molecules will undo the polarization.