2.1 Heat, Entropy, Calorimetry

Question 1

What is the equation modelling thermal conductivity. What are the units for thermal conductivity

Answer 1

Q/dt = (kA/L)dT

k (W/m*K)

Question 2

3 Fun Facts about Convection

Answer 2

1. The idea of “heat rises” is a mode of convection. Tme moving heat makes increases the temperature difference and allows more heat to exit
2. Convection is much more rapid in water than air. People die from hypothermia in 20C water, but live happily in 20C air
3. Designs to combat convection: Feathers, Double paned windows, fiberglass insulation trap air, preventing it from flying away and convecting heat away

Question 3

Define Thermal Radiation, and give an equation to model it

Amend the equation to model NET radiation

Answer 3

Def: Electromagnetic waves generated by oscillating electric charges in the atoms of an object

Eq: Q/dt = eσAT^4

NET: Q/dt = eeσA(T^4-T0^4)

Question 4

What is the Stefan-Boltzman Constant?

Answer 4

σ = 5.67E8
the constant of proportionality in the Stefan–Boltzmann law: “the total intensity radiated over all wavelengths increases as the temperature increases”

Question 5

What is a Solid Angle and what units do they have

Answer 5

Like a 3D radian: The ratio of a circle projected on a spheere to the radius square. (Steradians)

Ω = Asphere/R^2sphere = 4πr^2/r^2 = 4πSr

Question 6

What equation models entropy

Answer 6

dS = dQr/T [J/K] (where Qr is a reversible process)

Question 7

What equation models the heat flow through two parallel conductors

Answer 7

P = (k1A1 + k2A2)dt/L

Question 8

What equation models the heat flow through two conductors in Series?

Answer 8

T1(k1/L1 + k2/L2) = ThK1/L1 + TcK2/L2

Question 9

What is a calorie?

Answer 9

1cal = quantity of heat needed to change 1g of water by 1*C
1cal = 4.186J

Question 10

What is the specific heat capaicity of water?

Answer 10

c = 4186J/Kg