Question

The oven draws 1100 W of power, and you have determined that it heats with an efficiency of 51%. Using this information, determine the time t it would take to bring 240 mL of water from 25°C to 100°C . Note that 4.2 J of energy is required to raise the temperature of 1.0 mL of water by 1.0°C (the same as for the coffee above).

Answer 1

2.245 minutes

Step-by-step explanation:

Power, P = 1100 W

efficiency = 51%

T1 = 25°C

T2 = 100°C

ΔT = T2 - T1 = 75°C

Let the time taken is t.

Volume of water = 240 mL = 0.24 l

mass of water, m = volume of water x density = 0.24 x 10^-3 x 1000 = 0.24 kg

specific heat of water, c = 4200 J/kg °C

51 % of heat given by oven = heat gained by water

0.51 x 1100 x t = 0.24 x 4200 x 75

t = 134.76 seconds

t = 2.245 minutes

Thus, the time taken is 2.245 minutes.