A kettle with 2 litre water at `27^@C` is heated by operating coil heater of power 1 kW. The heat is lost to the atmosphere at constant rate `160 J//s`, when its lid is open. In how much time will water heated to `77^@C` with the lid open ? (specific heat of water = `4.2 kJ//^@C.kg)`A. 5 min 40 sB. 10 min 20 sC. 8 min 20 sD. 16 min 10 s

A kettle with 2 litre water at `27^@C` is heated by operating coil hea

1.	A kettle with 2 litre water at `27^@C` is heated by operating coil heater of power 1 kW. The heat is lost to the atmosphere at constant rate `160 J//s`, when its lid is open. In how much time will water heated to `77^@C` with the lid open ? (specific heat of water = `4.2 kJ//^@C.kg)`A. 5 min 40 sB. 10 min 20 sC. 8 min 20 sD. 16 min 10 s
Answer» Correct Answer - C Rate of heat gain =`1000-160=840J//s` `therefore` Required time = `(2xx4.2xx10^(3)xx(77-27))/(840)=500s` = 8 min 20 s

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