A friend who has just learned about dielectric insulators and capacitors is puzz
ID: 1349342 • Letter: A
Question
A friend who has just learned about dielectric insulators and capacitors is puzzled and asks tor your help "Heres my problem." she says, "suppose f charge up a capacitor to an electrical energy level of 1 J. The plates are disconnected from everything and theres a vacuum between them. Now I place an insulator with dielectric constant R = 3 between the plates. Im pretty sure that the energy stored in the capacitor should go down but Im not sure by how much. But even after I figure that out, the real puzzle is this what happens to the energy that was lost? Where did it go?" Can you help her?Explanation / Answer
Here ,
as dielectric constant , k = 3
for the isolated capacitor ,
charge on capacitor will be same
and new capacitance , C = 3 * Co
final energy = 1/(k) = 1/3
change in energy = 1/3- 1
change in energy = -2/3 J
the energy will go down by 2/3 J
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as the dielectric will be attracted by the capacitor ,
and energy will be transferred to the dielectric.