A 900pF capacitor is charged by 100V battery.
i.How much electrostatic force is stored by the capacitor?
ii.The capacitor is disconnected from the battery and connected to another 900pF capacitor.What is the electrostatic energy stored by the system?
iii.Where has the remainder of the energy gone?

Asked by sunil2791 | 18th Jun, 2017, 07:26: AM

Expert Answer:

begin mathsize 12px style left parenthesis straight i right parenthesis space Electrostatic space energy space stored space in space the space capacitor space is
straight E equals 1 half CV squared equals 1 half cross times 900 cross times 10 to the power of negative 12 end exponent cross times 100 squared equals 4.5 cross times 10 to the power of negative 6 end exponent space straight J

left parenthesis ii right parenthesis space When space the space capacitor space is space disconnected space and space connected space straight t space another space capacitor comma
the space net space capacitance space is
fraction numerator 1 over denominator straight C apostrophe end fraction equals 1 over straight C plus 1 over straight C equals 2 over straight C
straight C apostrophe equals straight C over 2
Therefore comma space the space energy space stored space is
straight E apostrophe equals 1 half cross times straight C over 2 cross times straight V squared equals 2.25 cross times 10 to the power of negative 6 end exponent space straight J

left parenthesis iii right parenthesis space The space remainder space of space the space energy comma space straight i. straight e. space left parenthesis 4 minus 2.25 right parenthesis equals 2.25 cross times 10 to the power of negative 6 end exponent space straight J space goes space in space charging space the space new space capacitor space
to space the space desired space level space as space there space is space no space external space source space now space available space to space provide space the space charges. end style

Answered by Romal Bhansali | 1st Nov, 2017, 01:13: PM

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