1.

The capacitance of a variable capacitor joined with a battery of 100 V is changed from 2muF to 10 mu F. What is the change in the energy stored in it ?

Answer»

`2xx10^(2) J`
`2.5 xx10^(2)` J
`6.5 xx10^(-2)J` J
`4 xx10^(-2)` J

Solution :The ENERGY stored in CAPACITOR of 2`mu`F.
`U_(1)= (1)/(2) xx2xx10^(-6)xx(100)^(2) =10^(-2)` J
The energy stored in capacitor of `10 mu F `
`U_(2) = (1)/(2)xx10xx10^(-6)xx(100)^(2)`
`U_(2) = 5xx10^(-2)` J
`:.` The change in stored energy
`U = U_(2)-U_(1)= 5xx10^(-2) - 1 xx10^(-2)`
`:. U = 4xx10^(-2) `J


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