Basic Thermodynamics ~ J. Pohl ©

www.THERMOspokenhere.com

When will the Teapot Whistle

You pour 1 liter of water into a thermally insulated, electrically heated teapot which you then plug in. The metal of the teapot is equivalent to 200 cm³ of water and the label of the teapot says it is rated at 1250 W.
i)How long will you have to wait for the water to boil and for the pot to whistle?
ii)Assume you get so involved in your thermo homework that you forget to pull the plug on the kettle, how long will the whistling of the teapot last?

Solution:  The system will be the water and the metal taken as its equivalence of water. The energy equation for these materials as they sit on the table is:

(1)(1)

Below left, the energy term, E, for the sake of beginners, is expanded to its internal energy, kinetic energy and potential energy components. Also, right-of-equality, the sum of works term, ΣW-dot is expanded.

(2)(2)

When will the Teapot Whistle

When you turn it on, a thermally insulated, electrically heated teapot pour contains 1 liter of water at @25°C. The metal of the teapot is equivalent to 200 cubic centimeters of water and the label of the teapot says it is rated at 1250W. How long will you have to wait for the water to boil and for the pot to whistle?