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![[Post New]](/templates/default/images/icon_minipost_new.gif) 17 Jul 2007 16:44:10 IST
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Any1 who is interested in scratching his head is most welcome........ And let me tell u 1 thing before I proceed to my head-scratching problem.....that whoever expresses his/her views in this regard will be rewarded wid SALUTES n THUMBS UP... the ques. is ... A parallel plate capacitor is connected to a battery. Would u do +ve or -ve work in moving the plates closer???? REPLY AS SOON AS POSSIBLE.
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17 Jul 2007 17:01:10 IST
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Arre yaar ......... is there nobody who can get it????????
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17 Jul 2007 17:14:27 IST
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the force bw the plates is attractive ,
so for the plates to be moved closer so as to not inc their kinetic
energy from 0, we will need a force dat is opp to the direction of the
displacement of the plates as they r moved closer
hence the work done wud be negative
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IIT JEE -2007 FRESHY
JOINING IN WID CHEM ENGG BTECH
IIT ROORKEE
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17 Jul 2007 18:39:17 IST
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The work done is zero.
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17 Jul 2007 19:03:49 IST
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yes the work done is negative 'coz force is attractive and you are not allowing any acceleration. but now look at this. energy of capacitor=1/2 c v^2 for the process, final -initial energy is=1/2v^2(c2-c1) but c2>c1 so energy has increased.......so some agent must have done the work.......so is our work done positive? if we reason properly, it is the attractive force betn plates doing this work....so our work done is indeed negative.
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ameya s,
1 yr
iit bombay.
if you ever want to help me clean my room, go STUDY NOW!!! |
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17 Jul 2007 19:28:04 IST
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Energy in a capacitor = CV2/2 Final energy = CfV2 / 2 Initial energy = CiV2 / 2 Change in energy = V2 / 2 * (Cf - Ci) If we are moving the plates closer we ar increasing the capacitance. .: Cf - Ci > 0 .: Change in energy > 0 .: Work done by external agent < 0
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18 Jul 2007 08:53:55 IST
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hey joyfrancis......
i fail to see reason wid ur last statement
change in energy>0
so why is work done by external agent <0???
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ameya s,
1 yr
iit bombay.
if you ever want to help me clean my room, go STUDY NOW!!! |
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18 Jul 2007 13:11:12 IST
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In my correspondence it says the correct answer to this is -ve workdone.
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18 Jul 2007 13:19:30 IST
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@joyfrancis,
even I wanna know why
change in energy>0 would imply
workdone by external agent<0 ????
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