`100` capacitors each having a capacity of `10 muF` are connected in parallel and are charged by a potential difference of `100 kV`. The energy stored in the capacitors and the cost of charging them, if electrical energy costs `108` paise per `kWh`, will be

Options

A. `10^(7)` joule and `300` paise
B. `5 xx 10^(6)` joule and `300` paise
C. `5 xx 10^(6)` joule and `150` paise
D. `10^(7)` joule and `150` paise

Answer

C

Explanation

Energy stored in the capacitor `= (1)/(2) CV^(2) xx 100`
`= (1)/(2) xx 10 xx 10^(-6) xx (100 xx 10^(3))^(2) xx 100 = 5 xx 10^(6) J`
Electric energy costs
`= 108` Paise per `WH = (108 Paise)/(3.6 xx 10^(6) J)`
`:.` Total cost of charging `= (5 xx 10^(6) xx 108)/(3.6 xx 10^(6)) = 150` Paise