Chapter 20, Problem 28PS

Interpretation Introduction

Interpretation: The efficiency of the microwave oven by comparing energy consumption with energy required to raise the water temperature should be determined from the given data.

Concept introduction:

Microwave oven: Conversion of electric energy into microwave energy is the basis of microwave oven. It consumes lesser energy than gas stove, but cost will be higher for microwave oven usage.

$\text{\%}\text{efficiency}\text{=}\frac{\text{energy}\text{absorbed}\text{by}\text{water}}{\text{energy}\text{released}\text{by}\text{the}\text{hot}\text{plate}}$

$\begin{array}{l}\text{Energy}\text{absorbed}\text{by}\text{water}\text{in}\text{joules}\text{=}\text{mass}\text{of}\text{the}\text{water(g)×}\text{ΔT}\text{°C}\text{×}\frac{\text{4}\text{.18}\text{J}}{\text{g}\text{°C}}\\ \text{Energy}\text{released}\text{by}\text{hot}\text{plate}\text{in}\text{joules}\text{=}\text{Total}\text{hot}\text{plate}\text{wattage}\text{(watts)×time(s)}\text{×}\left[\frac{\text{1}\text{J}/\text{s}}{\text{watt}}\right]\end{array}$