An immersion heater with electrical resistance `7Omega` is immersed in 0.1 kg of water at `20^(@)C` for 3 min. If the flow of current is 4 A, what is the final temperature of the water in ideal conditions ? (Specific heat capacity of water `= 4.2 xx 10 ^(3) Jkg ^(-1) K ^(-1))`

Options

A. `28^(@)C`
B. `48 ^(@)C`
C. `52 ^(@)C`
D. `68^(@)`

Answer

D

Explanation

`I ^(2) RT = ms Delta t `
`implies (4) ^(2) xx 7 xx 3 xx 60 = 0.1 xx 4.2 xx 10 ^(4) xx [T - (20^(@) + 273) ]`
`therefore T = 341 K = 68^(@) C`