Physics
WAEC 1993
How long does it take a 750 W heater operating at full rating to raise the temperature of 1 kg of water from 40
oC to 70
oC? (Take the specific heat capacity of water as 4200 J kg
-1 K
-1 and neglect heat losses).
-
A.
84s
-
B.
112s
-
C.
168s
-
D.
280s
-
E.
616s
Correct Answer: Option C
Explanation
div class="eq-c">pt = mcθΔ; t =
mcθΔ/p
=
1 x 4200 x (70 - 40)/750
= 168s
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