Topic: Thermal Physics PHYSICS 231schatz/PHY231/Lectures/lecture_thermal2_post.pdfunderstood the...
Transcript of Topic: Thermal Physics PHYSICS 231schatz/PHY231/Lectures/lecture_thermal2_post.pdfunderstood the...
PHYSICS 231 Topic: Thermal Physics
Current Assignments • Homework Set 8 open - due Thursday, Mar
24, 11pm • Next week Thursday, March 31, midterm
exam 2. – Topics: Momentum, Circular motion, rotation,
gravity, solids and fluids – As usual:
• No homework due during exam week • Review lecture Tuesday before exam
– Did you start your equation sheet?
4/4/11 Physics 231 Spring 2011 2
Key Concepts – Temperature (atomic picture, kinetic energy,
scales)
– Mole, atomic mass number
– Thermal expansion of solids (linear expansion of volume and length)
– Ideal gas law
– PV diagrams for constant V, P, or T
– Work done on gas (what does it do, calculation, and extraction from PV diagram)
4/4/11 Physics 231 Spring 2011 3
Key Equations • Note that these are only useful once you
understood the concepts and can derive equations that apply to a specific problem
• Thermal energy
• Temperature (K)-energy:
• T (in K) = TC (in 0C) + 273
• TC=5/9 (TF – 320)
• Be able to convert grams in moles …
4/4/11 Physics 231 Spring 2011 4
€
Eth = NKavg = N 12mvrms
2
€
Kavg =32kBT
Key Equations • Note that these are only useful once you
understood the concepts and can derive equations that apply to a specific problem
• Volume thermal expansion
• Linear thermal expansion
• Ideal gas law
• Work done on gas (or area under P(V) curve)
4/4/11 Physics 231 Spring 2011 5
€
ΔV = βViΔT
€
ΔL = αLiΔT
€
PV = NkBT
€
W = PΔV
Simulation
4/4/11 Physics 231 Spring 2011 6
http://www.google.com/url?sa=t&source=web&cd=1&sqi=2&ved=0CBgQFjAA&url=http%3A%2F%2Fwww.colorado.edu%2Fphysics%2Fphet%2Fprojects2%2Fidealgas%2Fidealgas.jnlp&rct=j&q=ideal%20gas%20law%20demonstration&ei=D3GLTaD2EKGG0QHAu_SIDg&usg=AFQjCNEiwoEr9sbr_PbikTM9SCTMwdgZXA&sig2=jZ0U8mV-eBYYB6ZOnNrnAw
Speed and Kinetic Energy of Gas Molecules
Slide 12-17
Two containers of the same gas (ideal) have these masses and temperatures: • Which gas has
atoms with the largest average thermal energy?
• Which container of gas has the largest thermal energy? A. P, Q B. P, P C. Q, P D. Q, Q
Checking Understanding
Slide 11-21
Two containers of the same gas (ideal) have these masses and temperatures: • Which gas has
atoms with the largest average thermal energy?
• Which container of gas has the largest thermal energy? A. P, Q B. P, P C. Q, P D. Q, Q
Answer
Slide 11-22
Volume check
• 1 m3 equals:
A: 100 cm2
B: 1000 cm2
C: 10,000 cm2
D: 100,000 cm2
E: 1,000,000 cm2
4/4/11 Physics 231 Spring 2011 10
Phases of Matter
Slide 12-16
Thermal expansion
4/4/11 Physics 231 Spring 2011 12
Clicker question
• To fit the ball through the hole does one have to: – A: Heat the ball
– B: Cool the ball
4/4/11 Physics 231 Spring 2011 13
Clicker question
• To fit the ball through the hole one must: – A: Heat the plate with the hole
– B: Cool the plate with the hole
4/4/11 Physics 231 Spring 2011 14
Clicker question
4/4/11 Physics 231 Spring 2011 15
2 materials bonded (glued) together
Aluminum
Steel
What happens to the stick when heated: A: Stays straight, gets longer B: Stays straight, gets shorter C: Bends upward D: Bends downward E: remains unchanged
Water is different
4/4/11 Physics 231 Spring 2011 16
Quiz
• When increasing the number of particles in the box
A: Pressure increases B: Pressure decreases
4/4/11 Physics 231 Spring 2011 17
Quiz
• When increasing the temperature of the gas in the box
A: Pressure increases B: Pressure decreases
4/4/11 Physics 231 Spring 2011 18
Quiz
• When increasing the volume (size) of the box while leaving the same amount of gas inside
A: Pressure increases B: Pressure decreases
4/4/11 Physics 231 Spring 2011 19
Quiz
4/4/11 Physics 231 Spring 2011 20
m
Gas
Gas pressure is A: same as outside pressure B: higher than outside pressure C: lower than outside pressure
Quiz
4/4/11 Physics 231 Spring 2011 21
m
Gas
When heated, gas pressure will A: stay the same B: increase C: decrease