Question

1. The textbook states, "Common household appliances such as dishwashers, microwave ovens, refrigerators, humidifiers, clothes dryers, toasters, water heaters, irons, and pressure cookers rely on principles of thermodynamics for their operation." (Hagen, pg 186) Choose one of these, or another household appliance, and describe what thermodynamic principles are at work. 2. You are going on a long road trip and want to take a mug of coffee with you. You would like the coffee to stay as warm as possible for the longest amount of time. What kind of coffee mug would you take with you? Discuss the mug material, size, and other factors that would affect heat transfer (which can occur by conduction, convection, and radiation).

Answer 1

1) Let's take pressure cooker as an example. The lid is closely tight and there is no loss of energy. The vapor pressure rises with temperature however it has nowhere to go. The pressure can't relieve itself by pushing the lid up and escaping. The energy that has been put into heating the food and water stays in the pot, and consequently we can achieve higher temperatures inside the pot. There exist a dependent relation between pressure and temperature inside the pot.

2) The material of mug should be made in such a way to minimize losses due to radiation and conduction. . To keep the drinks hot it minimizes heat transfer due to conduction and radiation. Convection is not included because convection keeps the temperature in a liquid even