1.

When two capacitors are connected in series and connected across 4kV line, the energy stored in the system is 8 J. the same capacitors, if connected in parallel across the same line, the energy stored in 36 J. find the individual capacitances.

Answer»

SOLUTION :`E=(1)/(2)CV^(2)`
finding `C_(1)+C_(2)=4.5xx10^(-6)F`
finding `C_(1)+C_(2)=4.5xx10^(-12)`
Final answer `C_(1)3muF`
and `C_(2)=1.5muF`
Detailed
`E_(S)=(1)/(2)C_(S)V^(2)=(1)/(2)[(C_(1)C_(2))/(C_(1)+C_(2))]V^(2)` . . (1)
`E_(p)=(1)/(2)C_(p)V^(2)=(1)/(2)[C_(1)+C_(2)]V^(2)`. . (2)
`8=(1)/(2)[(C_(1)C_(2))/(C_(1)+C_(2))]xx(4xx10^(3))^(2)`. . (4)
`36=(1)/(2)[C_(1)+C_(2)]xx(4xx10^(3))`. . (5)
on SOLVING equation (4) and (5) we get
`C_(1)=3muF,C_(2)=1.5muF`.


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