B.1 Heat Transfer

==internal energy==: the total random kinetic energy of the particles of a substance, plus the total intermolecular potential energy of the particles: U = total random kinetic energy + total intermolecular potential energy.

==specific heat capacity==: the energy required to increase the temperature of a unit mass of the body by one kelvin.

==Specific latent heat==: , L, is the energy required to change the phase of 1 kg of a substance at constant temperature and pressure. ==Fusion==: melting/freezing. ==vaporisation==: vaporize/condense.

conduction/convection/radiation

higher the temperature, smaller \(\lambda_\text{max}\)

==Intensity== is the power of radiation received or emitted per unit area.

Energy density = energy per unit volume Specific energy = energy per unit mass

B.2 Greenhouse

![[_resources/Pasted image 20251008201824.png]]

Black Body

definition: - emmisivity: \(e=1\)

Wien’s displacement Law

只要有温度，都在向外发射波

从波长推算温度

high T -> higher radiation -> higher intensity + Wien displacement law -> lambda_max smaller

Energy Balance

income intensity = reflect intensity => same temperature

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B.3 Ideal Gas definition

1. \(E_p=0\) (most important, fundamental assumption): no intermolecular force
2. \(F=0\)
   • what kind of gas can be determined as ideal gas
     • density small
3. high temperature, low pressure -> \(E_k>>E_p\)

ideal gas: - pressure: particles collide with wall -> momentum change -> make force - low density -> less frequency of colliding with wall -> less pressure

greenhouse effect definition ![[_resources/Pasted image 20250913205057.png]]

B.5 Circuits

1. Know the net voltage
2. Treat the whole circuit as the simplest one
3. Get the net resistor
4. Get net current
5. do it recursively for each sub module, with each net voltage or current refers to value in between两端

for emf and internal resistance: \[ V_\text{terminal} = \mathcal{E} - I_\text{net} \times r_\text{internal} \]

voltage at one point:

\[ V = V_\text{supply} \times \frac{\text{net R before the point to supply}}{\text{total R of the branch}} \]

常见敌人

gives you a spectral intensity vs. wavelength graph graph, higher temperature makes the hill left up:

![[_resources/Pasted image 20260218165322.png]]

draw on an ==Hertzsprung-Russell diagram==: 1. locate the correct temperature 2. go vertical until hit the nearest radius slope line

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对热导率公式的理解：\(\frac{\Delta Q}{\Delta t}=kA\frac{\Delta T}{\Delta x}\) ，其中\(\frac{\Delta T}{\Delta x}\) is temperature gradient/slope (how rapidly temperature changes with distance)

\(\bar{E_k} = \frac32 k_BT\) means the average kinetic energy of a single molecule in an ideal gas; 常见坑：temperature is equivalent to the average kinetic energy of the ideal gas, does not relate to total kinetic energy

burning coal: Chemical energy from coal into internal energy of water; Internal energy transferred to kinetic energy of turbine; Turbine’s kinetic energy transferred to electric power in the generator.

finding molecule’s average speed from temperature and molar mass - get average kinetic energy (J per molec) from Kelvin - use \(\frac{1}{2}mv^2\) to find \(v\). Here \(m\) is \(\frac{\text{molar mass}}{\text{Avogadro constant}}\) to get mass of one molecule

potential energy on gas: - distance between molecules (density), bigger density -> bigger potential energy - number of molecules (more particles, more interaction)