week 4 Flashcards
first law of thermodynamics
energy can be neither created or destroyed, only its form can change
what is a microscopic form of energy
form of energy of a system related to the molecular activity of the system
what does microscopic form of energy depend on
temperature
what is the sum of all microscopic form of energy called
internal energy
what is the internal energy
the sum of all microscopic forms of energy of a system
how does internal energy increase or decrease
it increases or decreases with temperature
how do you find out the total energy of a thermodynamic system
internal energy PLUS kinetic energy PLUS potential energy
what is the formula first law of thermodynamics for a closed system
the total energy in the system MINUS total energy leaving the system
sign convention for - work done on the system (by surroundings) is
- negative (compression)
sign convention for - work by the system (on surroundings)
+ positive (expansive)
sign convention for - heat transfer from surroundings to the system is
+ positive (heating)
sign convention for - heat transfer from system to surroundings is
- negative (cooling)
what is the conservation of mass in a closed system
mass is conserved and does not cross boundaries (remaining unchanged)
what is the conservation of mass in a open system
mass does cross boundaries, which we need to keep a track off
what is ‘work flow’ in an open system
when mass crosses boundaries ‘work energy’ is needed to push mass into or out the system. this work is called ‘work flow’
what is a nozzle
device that increases the velocity of fluid at the expense of pressure
what is a diffuser
device which increases pressure of a fluid by slowing it down
what is a turbine
used to drive electric generator in steam, gas or hydroelectric power plant.
what does the work for the turbine and is it positive or negative work
turbines work is done by the fluid (positive work)
what is a compressor
used to compress air
what does the work for a compressor and is it a positive or negative work
work is done on the fluid to increase its pressure (negative work)
