lecture 4

Question 1

entropy always

Answer 1

increases with time

Question 2

work can easily be transformed into

Answer 2

heat but heat cannot easily be transformed into work

Question 3

what makes a process irreversible

Answer 3

heat is generated

Question 4

entropy =

Answer 4

change in heat/temperature

Question 5

why does generating heat make a process irreversible

Answer 5

heat to work is difficult work to heat is easy

it generates entropy

Question 6

entropy is a property of a

Answer 6

substance

Question 7

more reversable a process is

Answer 7

the lower the entropy increase will be

Question 8

entropy is the arrow of time

Answer 8

entropy always increases no matter what you do if you decreases entropy in one place you are increasing it by a greater amount somewhere else

Question 9

friction prevents

Answer 9

an reversible process exsisting

Question 10

entropy decreases

Answer 10

when a system is cooled

Question 11

entropy increasse

Answer 11

when heat is added to a system

Question 12

change in entropy =

Answer 12

irreversibility change + change in heat/temp

Question 13

There is an entropy increase associated

Answer 13

with heat transfer, and friction, but not with work.

Question 14

for adiabatic process entropy increase =

Answer 14

0

Question 15

for a reversable process

Answer 15

ds = dq/T

Question 16

substituting change in dq = Tds into first law

Answer 16

Tds = du +pdv
ds = du/T + dpv/T

Question 17

change in enthalpy =

Answer 17

Tds - vdp

Question 18

entropy for solids and liquids

Answer 18

ds = du/T + pdv/T
dv = 0 and du =cvdT
ds = cv dT/T = cv lnT2/T1

Question 19

entropy for ideal gas

Answer 19

in the LBoT

Question 20

why for the given change in temperature for gas the entropy change greater than a solid

Answer 20

as extra component R =lnv2/v1

see LBoT for gas

Question 21

isentropic process is one where

Answer 21

entropy does not change

Question 22

draw the temperature entropy diagram for steam

Answer 22

see powerpoint

Question 23

draw the temperature entropy diagram for an ideal gas

Answer 23

see powerpoint

Question 24

if isentropic process describe the arrow of a pressure increase

Answer 24

straight arrow upwards

Question 25

if non isentropic process describe the arrow of a pressure increase

Answer 25

arrow will move to the right as entropy always increases

Question 26

compression

Answer 26

pressure increase (compressor)

Question 27

expansion

Answer 27

pressure decreases (turbine)

Question 28

isentropic process is

Answer 28

the most efficient

Question 29

efficiency =

Answer 29

what you want/what you pay for

Question 30

efficiency should always be

Answer 30

less than one