Answer:
(c) 10.8 min
Explanation:
The energy that must be supplied by the heating element is W = Pxt, where is the power in watts multiplied by the time. By the energy conservation law, the energy is the heat, q, absorbed by the water to raise its temperarure by a change in temperature ΔT, and can be calculated from the equation:
q = mcΔT
ΔT = 95 ºC - 12 ºC = 83 ºC = 83 K ( because ºC is linearly related to K)
q = 1.5 kg x 4.18 kJ/kg x (83 K) = 520.4 kJ = 5.2 x 10⁵ J
Thus
W = P x t ⇒ t = W/P
t = 5.2 x 10⁵ J / 800 J/s = 650 s x 1 min/ 60s = 10.8 min
