lecture_jan18_upload

lecture_jan18_upload - A good free book: Sustainable...

Info iconThis preview shows pages 1–15. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: A good free book: Sustainable Energywithout the hot air , by David MacKay www.withouthotair.com (get this book for free !) You can also see a 10-page synopsis for quick- read Lecture 5 Forms of energy relevant to climate: Kinetic energy: the ability to do work due to motion. Gravitational (or potential) energy : the ability to do work through changes in a body's location within a gravitational field. Thermal energy (or heat): the ability to do work through the release of heat. Electromagnetic wave energy: energy embedded in electromagnetic wave motion (such as light, microwaves, or x-rays). Chemical energy: the ability to do work via a chemical interaction (i.e., change in molecular structure) Inside a hot gas, individual molecules move at rapid rate. Inside a hot solid, individual atoms vibrate vigorously about their undisturbed positions. KE and Elastic PE But all is disordered and hidden. Thermal energy is related to motion of microscopic parts, not of the whole. Thermal energy vs. Mechanical energy Some confusion between these terms: Energy Concepts Simple machines Ideal Machine: Energy input = Energy output Work input = F x d input = F x d output = Work output Power Concepts Heat and Temperature are not the same thing Heat: related to the total kinetic energy of all the molecules Temperature: is not energy but a measure of the average kinetic energy of the molecules The boxes has the same temperature as the average (indicated by the length of the arrows) is the same but there are more molecules on the right hand one, and hence it contains more Heat. Different materials have different capacities for heat Add the same energy to different materials, and youll get different temperature rises Quantified as heat capacity Water is exceptionally high, with 4,184 J/kg/C Most materials are about 1,000 J/kg/C (including wood, air, metals) A useful definition of Heat Capacity is Specific Heat The specific heat of a substance is the heat required in calories to raise the temperature of 1 gram by 1 degree Celsius. Water has a higher heat capacity than Copper and we can see what the implications of this is. What would be the change in temperature if 2 kg of liquid water was heated with 10,000 J of heat? Q (heat) = mc T m = mass (in kg) c = specific heat- this is a measure of how much heat a material can store T = change in temperature 10000 J = 2kg x 4186 x ( T) T = 10000 /(2 x 4186) T = 1.2 degrees C Heat and Work Besides the heat capacity of a substance, we also find that for a change of phase energy is either absorbed or released. This energy flow happens even though there is no change in temperature....
View Full Document

Page1 / 67

lecture_jan18_upload - A good free book: Sustainable...

This preview shows document pages 1 - 15. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online