WAEC - Physics (1993 - No. 51)
How long does it take a 750 W heater operating at full rating to raise the temperature of 1 kg of water from 40oC to 70oC? (Take the specific heat capacity of water as 4200 J kg-1 K-1 and neglect heat losses).
84s
112s
168s
280s
616s
Paliwanag
div class="eq-c">pt = mcθΔ; t =
mcθΔp
= 1 x 4200 x (70 - 40)750
= 168s