Question

A electric kettle ( rated accurately at `2.5 kW`) is used to heat `3 kg` of water from `15^(@)C` to boiling point . It takes `9.5 min`. Then the amount of heat that has been lost is
A. `3.5 xx 10^(5) J`
B. `7 xx 10^(8) J`
C. `3.5 xx 10^(4) J`
D. `7 xx 10^(8) J`

Answer 1

Correct Answer - A
Energy consumed in `9.5 min ` is
`2.5 xx 1000 xx 9.5 xx 60 J = 1425000 J`
Heat usefully consumed is
` 3 xx 4.2 xx 1000 xx (100 - 15 ) J = 1071000 J`
Loss `= 3.54 xx 10^(5) J`