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. `85%`
D. `95%`

Answer

C

Explanation

When charge
Energy `= 15 xx 10 xx 8` Wh
When discharge
Energy `= 14 xx 5 15` Wh
Energy `=14 xx 5 xx 15` Wh
`eta = (14 xx 5 15)/(15 xx 10 xx 8) = 7/8 = 87.5%`