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International Baccalaureate · IB Diploma · Physics · HL หัวข้อ 9 4:02 การบรรยายภาษาอังกฤษ · คำบรรยายภาษาอังกฤษ + 中文 ลอยตัวบนภาพ
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Compressing a gas can warm it even without a heater.
压缩气体即使没有加热器也能使其升温。
Work is another path for energy transfer into the system.
做功是能量传入系统的另一种途径。
Internal energy is a property of the chosen system.
内能是所选系统的性质。
Heat and work describe energy transfer across its boundary.
热量和功描述了跨越其边界的能量传递。
For an ideal monatomic gas, internal energy depends on temperature and amount.
对于理想单原子气体，内能取决于温度和物质的量。
Adiabatic: A process with no heat transfer.
绝热：没有热量传递的过程。
Internal energy: Total microscopic kinetic and potential energy of a system.
内能：系统总微观动能和势能之和。
State a sign convention before using the first law.
在使用热力学第一定律之前，先说明符号约定。
Here, change in internal energy equals heat into the system minus work done by the system.
此处，内能的变化等于系统吸收的热量减去系统对外做的功。
Expansion work can reduce internal energy when no heat enters.
当没有热量进入时，膨胀做功会降低内能。
In the lab: Identify whether a process is isothermal, adiabatic or at constant volume.
在实验室中，判断过程是等温、绝热还是等容。
On a pressure-volume graph, area under the process curve gives work done by the gas.
在压强-体积图上，过程曲线下方的面积表示气体所做的功。
The path matters for work even when endpoints match.
即使端点相同，路径对做功也有影响。
Known: a gas gains 300 J by heating and does 120 J of work.
已知：气体吸热获得 300 J，并对外做功 120 J。
With delta U equal to Q minus W, delta U equals 300 minus 120, which is 180 J.
由 ΔU 等于 Q 减 W，ΔU 等于 300 减 120，即 180 J。
For adiabatic compression, Q equals 0 and the work done by the gas is negative, so delta U is positive.
在绝热压缩中，Q 等于 0，气体所做的功为负，所以 ΔU 为正。
Your turn: A gas gains 500 J of heat and does 200 J work.
请作答：某气体吸收 500 J 热量，对外做功 200 J。
Find internal-energy change.
求内能变化量。
Pause the video and work it out.
请暂停视频，自己算一算。
Check: the heat in minus the work done, 500 minus 200, is an increase of 300 joules.
核对：吸收的热量减去对外做功，500 − 200，内能增加 300 焦。
Adiabatic does not mean constant temperature.
绝热过程并不意味着温度恒定。
Use the stated sign convention; some courses write work done on the gas with the opposite sign.
请采用文中所述的符号约定；部分课程中，对气体做功的符号与此相反。
Not true: Every adiabatic process has constant temperature.
不正确。 并非所有绝热过程温度都保持不变。
Adiabatic fixes heat transfer (Q = 0), not temperature.
绝热过程固定的是热量传递，即Q等于零，而非温度。
An adiabatic compression raises temperature - bicycle pumps warm up - and an adiabatic expansion lowers it.
绝热压缩会使温度升高，例如自行车打气筒会发热；而绝热膨胀则会使温度降低。
Isothermal, not adiabatic, is the constant-temperature process.
等温过程才是恒温过程，而非绝热过程。
Internal energy is a property of the chosen system.
内能是所选系统的性质。
State a sign convention before using the first law.
在使用热力学第一定律之前，请明确符号约定。
Watch for: adiabatic does not mean constant temperature.
请注意：绝热过程并不意味着温度恒定。
A gas gains 800 joules of heat and does 350 joules of work.
气体吸收800 J的热量，对外做功350 J。
Find the change in internal energy.
求内能的变化量。
Adiabatic means no heat transfer, not constant temperature.
绝热过程意味着没有热量传递，而非温度恒定。
The result is an internal-energy change of 450 joules.
结果是内能变化450焦耳。
Of the 300 joules of heat put into the gas, 120 joules leave as work done by the gas. The remaining 180 joules raise its internal energy.
输入气体的300焦耳热量中，有120焦耳以气体对外做功的形式离开，其余180焦耳使其内能增加。
A gas is compressed adiabatically by 150 J, then releases 40 J heat at fixed volume.
气体被绝热压缩，外界对气体做功150 J，随后在定容条件下放出40 J热量。
Find total internal-energy change using work done by gas positive.
若规定气体对外做功为正，求内能的总变化量。
Compression has Q equal to 0 and W equal to minus 150 J, giving plus 150 J.
压缩过程中 Q 等于 0，W 等于 −150 J，得到 +150 J。
Cooling has Q equal to minus 40 J and W equal to 0, giving minus 40 J.
冷却过程中 Q 等于 −40 J，W 等于 0，得到 −40 J。
The total change is plus 110 J.
总变化为 +110 J。
Keep one sign convention throughout.
全程要保持同一种符号约定。
Pause and check yourself. Explain each point on screen in your own words, then change one number in the last example and say which assumption must still hold.
暂停一下，自我检查：用自己的话解释屏幕上的每个要点，再改动最后一个例子中的一个数字，说明哪个假设仍然必须成立。