Physics Midterm 1 Chapter 4 2

Front 1

what is required for heat flow? what are the three modes of heat transfer?

Back 1

radiation, convection, conduction

Front 2

which mode of transfer is dominant in: solids,fluids

Back 2

solids: conduction

liquids: convection

Front 3

what factors determine the conductive heat flow?

Back 3

area

difference in T

thermal conductance of material

Front 4

what is thermal conductivity? does it change from one material to another? for a given material does it depend on the geometry?

Back 4

its the measure of a materials ability to conduct heat, the larger K is, the more efficient a substance conducts heat

Front 5

What is R-value? how does it depend on conductivity? is it a material property?

Back 5

it gives a measure of that materials resistance to the flow of heat, its what helps rate the insulating quality of materials, larger R value the better at insulating

Front 6

what is convection?

Back 6

heat flow by the movement of a fluid

Front 7

does heat transfer always require a medium?

Back 7

no radiation doesnt

Front 8

what are thermal radiations made of?

Back 8

electromagnetic waves

Front 9

what is prevost theory on heat exchange through thermal radiations?

Back 9

-all objects radiate energy at all temp except at absolute zero

-rate of radiation depends on temp of the radiating object alone

-objects simultaneously emit and absorb radiation

-Temperature of the object changes with time due to this exchange and will become a constant only after the object reaches thermal equilibrium with the surrounding.

Front 10

what determines the quality of energy? give ex of high quality energies

Back 10

?

Front 11

is thermal energy a high quality energy?

Back 11

?

Front 12

is it possible to convert all of the energy in random motions to energy in org motion? how about the other way?

Back 12

its possible to convert ordered motions to disordered, they eventually do, but they can be converted the other way around

Front 13

the process of converting directed kinetic energy to random kinetic energy is irreversible. which law of thermodynamics explains why?

Back 13

order-disorder

Front 14

what is the first law of thermodynamics? what is the second?

Back 14

order-disorder

entropy

Front 15

what is entropy? can the entropy of a closed system ever decrease?

Back 15

it is the measure of a disorder of a system

?

Front 16

what is a heat engine? is it possible to convert a heat engine that converts all of thermal energy to mechanical work?

Back 16

a heat engine is a device that converts random thermal energy into organized mechanical energy

Front 17

what is the definition for the efficiency of a heat engine? is it possible to construct a perfect heat engine that is 100% efficient?

Back 17

-its the ratio of the mechanical energy delivered to total energy ex

-no

Front 18

what is a carnot engine? what is carnot efficiency?

Back 18

-an engine with maximum efficiently allowed by the laws of physics

-CE is related to the temp difference between the source and sink

Front 19

what determines the carnot efficiency of a carnot engine?

Back 19

e=1- (Tc/Th)

Front 20

under what conditions will the carnot efficiency approach 100%?

Back 20

?

Front 21

what is cogeneration?

Back 21

waste heat from the power generation plants are put to use for heating in industrial or residential sectors

Front 22

heat pumps and refrigerators

Back 22

-transfer heat from cooler to hotter systems

-heat pumps can provide efficient heating by using small amounts of high quality energy to transfer large amounts of heat