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

Answer:

134.75935 seconds

Explanation:

m = Amount of water = 240 mL

c = Specific heat of water = 4.2 J/mL °C

$\Delta T$ =  Change in temperature = $100-25=75$

t = Time taken

P = Power = 1100 W

E = Pt

Efficiency = 51 %

So, Energy = 0.51Pt

As energy is conserved

Q = 0

$\\\Rightarrow -mc\Delta T+E=0\\\Rightarrow -mc\Delta T+Pt=0\\\Rightarrow -240\times 4.2(100-25)+0.51\times 1100t=0\\\Rightarrow t=\frac{240\times 4.2(100-25)}{0.51\times 1100}\\\Rightarrow t=134.75935\ s$

The it takes to raise the temperature is 134.75935 seconds