Physics 122
Terms
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- System
-
amount of matter enclosed by boundaries and surfaces
described by P, V, T - Heat resevoir
- Large seperate system with unlimited heat capacity; heat entering/leaving system comes from or goes to it
- State
- specific combination of variables P,V,T
- Equation of State
- Relates the state variables
- Process
- A change in the system or state variables
- Zeroth law
- if T1=T2 and T2=T3 then T1=T3
- First Law
-
Conservation of Energy
Q = /_\U + W - When heat enters system
- Temp increases, change in U is positive
- If w positive
- System does work
- If w negative
- System is worked upon
- Heat leaves
- temp decreases, delta U is negative
- Work done
- area under the curve
- Isothermic
-
Change done under constant temperature; delta U = 0 so
Q = W - Isobaric
-
Change done under constant pressure
W = p*deltaV - Isometric
-
Change done under constant volume
W=0; Q = deltaU - Adiabatic
-
No heat transfered in or out
Q=0 so -W = deltaU
(steeper than isotherm) - entrophy
- measure of disorder
- reversible process
- a system returns to its initial state by tracing its initial process backwards
- Second law
-
heat will not flow spontaneously from a cold object to a hot object
all natural processes move to a state of higher disarray - Engines and pumps as relates to the first law
- Total heat input = total heat output (and work)
- Heat engine
-
converts heat E to work; takes h from hot resevoir, does work, expells excess heat into cold resevoir
want to max work - thermal pump
- Transfers heat from cold resevoir to hot
- coefficient of performance
- measures efficiency of therm pump for refridg and heat pump
- carnot cycle
-
most efficient cycle for heat engine,
2 adiabatic and 2 isothermal processes - carnot efficiency
- deals in temperatures, max eff for heat engine !in kelvin
- Third law
- As system approaches 0 K, all process begin to stop, entrophy reaches minimum value
- simple systems
- single bodies of mass
- periodic motion
- motion that repeats itself
- equilibrium
- resting point of the system
- amplitude
- maximum displacement of mass
- period
- length of time for one cycle
- frequency
- number of cycles per unit time
- simple harmonic motion
- motion that can be described sinusoidally
- if motion starts at 0
- sin
- if motion starts at displacement y=A
- cos
- angular frequency
- how fast object is oscillating in rad/s
- phase shift
- change in initial displacement
- wave
- disturbance passing through medium carrying energy
- periodic wave
- continuous wave that moves sinusoidally
- wavelength
- spatial length of one cycle
- traveling wave
- dependent on time and displacement
- +/-
-
+ if wave moves to left
- if wave moves to right - transverse wave
- particles oscillate perpendicular to wave
- longitudinal wave
- particles oscillate parallel to wave motion
- interference
- behavior of two waves in the same region
- Constructive interference
- amplitude of the waves is summed
- Destructive interference
- amplitude of waves is less than either individual, if same amp, cancel each other out
- reflection
-
wave strikes boundary and is reflected back into initial medium
-fixed - inverted
-free - wave is same - refraction
- wave bends when entering different medium, depends on speed change
- dispersion
- waves at different frequencies refract at different angles in a medium
- diffraction
- bending of waves around obstructions (if same or smaller size than wavelength)