A battery is charged at a potential fo 15 V for 8 h when the current folwing is 10A. The battery on discharge supplies a current of 5A fo 15h . The mean terminal voltage during discharge is 14V. The watt-hour efficiency of the battery is

Options

A. `80% `
B. `90%`
C. `87.5% `
D. `82. 5% `

Answer

C

Explanation

The power of the battery, when charged, is given by `P_(1) = V_(1)I_(1)` The electrical energy dissipated is given by `E_(1) = P_(1) t_(1)`
i.e ., `E_(1) = P_(1) I_(1) t_(1)= 15 xx 10 xx 8 `
=1200 Wh
Similarly, the electrical energy dissipated during the discharge of battery is given by
`E_(2) = V_(2) I_(2) t_(2) = 14 xx 5 xx 15 `
= 1050 Wh
Hence, watt-hour efficiency of the battery is given by
`eta = (E_(2))/(E_(1)) xx 100 = 0.875 xx 100 = 87 .5 % `