arning Goal:

practice Problem$-$Solving Strategy $11\mathrm{.}1$ Energy efficiency bblems.

ppose that you have left a $200-mL$ cup of coffee sitting until it s cooled to $30C,$ which you find totally unacceptable. Your crowave oven draws $1100W$ of electrical power when it is hning. If it takes $45s$ for this microwave oven to raise the mperature of the coffee to $60C,$ what is the efficiency of ating with this oven?

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Assess

Determine whether your answer agrees with your experience.

Part D

The oven draws $1100W$ 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 $240mL$ of water from $25C$ to $100C.$ Note that $4\mathrm{.}2J$ of energy is required to raise the temperature of $1\mathrm{.}0mL$ of water by $1\mathrm{.}0C($the same as for the coffee above$).$

Express your answer in seconds to two significant figures.

View Avallable Hint$($s$)$

$t=$

s