1.

An electric heater rated as (500 W and 200 V) raises the temperature of 1 kg water from `15^(@)C` to its boiling point in 15 min. the heat effeciency of the heater isA. 0.79B. 0.97C. 0.69D. 0.96

Answer» Correct Answer - A
Heat absorbed by water `=msDeltaT`
Heat supplied by heater`=vlt=Pt`
`therefore " " " Efficiency " =(msDeltaT)/(Pt)xx100`
By putting given value, efficiency `~~ 79 %`


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