Heater capacity in KW for heating 100 litre water with temparature raise of 40 deg. C ?

Answer 1

The first guy's answer is wrong. He used the wrong unit. It should've been Kile joules instead of joules. My answer is correct.

We know, the mass of 1 litre water = 1kg. So, 100 litre means 100 kg of water. Now,
mass, m = 100 kg
specific heat of water, S = 4200 J/kg/K
temp. difference, T2 - T1 = 40 C = 40 K
heat, Q = ?

We know, Q = mS(T2 - T1)
or, Q = 100 * 4200 * 40
or, Q = 16800 * 10 ^3 Joule
so, Q = 16800 kJ

1 kW = 1 kJ /s

as you did not mention any time, I will assume the time is 1 hour ( as it is in most cases for heat related problems ).

so, P = Q/t
or, P = 16800/3600 [ 1 hour = 3600 second ]
or, P = 4.667 kW

The heater capacity must be 4.667 kW [ assuming time = 1hour ]
(Ans.)

If the time is different, just do the last part of the calculation with the correct time.

Hope this was helpful.

Answer 2

Heat = mass*specific heat capacity*change in temp.
Therefore,
H = ms(t² - t)
=100*4.2*40
=
16800 joules
1 kW = 1000 W
=
1000J/S
but wat is the time??
if u give the time i'll give u the answer