(2)热量是有方向的量( Heat is directional quantity. eat addition is the transfer of heat into a system Heat rejection(放热) is the transfer of heat out of a system Formal sign convention heat addition is positive ' t heat rejection is negative,' (3)“ Adiabatic” means no heat is transferred “绝热”意味着没有热量传递。) (4 Heat transfer can change the state of the system. (传熟可以引起系统状态的变化
(2)热量是有方向的量(Heat is directional quantity. ) Heat addition (加热） is the transfer of heat into a system. Heat rejection（放热） is the transfer of heat out of a system. Formal sign convention: heat addition is positive, ‘+’ . heat rejection is negative, ‘-’ . (3) “Adiabatic ” means no heat is transferred （“绝热”意味着没有热量传递。）. (4) Heat transfer can change the state of the system. （传热可以引起系统状态的变化。）
2. j( Energy transfer by Work Work is the energy transfer associated with a force acting through a distance (1)功量也是传递中的能量 Work is also energy in transition We can have push-pull work(e.g in a piston-cylinder, lifting a weight), electric and magnetic work(e. g. an electric motor), chemical work, surface tension work, elastic work, a rotating shaft. (2)功量是有方向的量 Work is also directional quantity o
2.功 ( Energy transfer by Work ） Work is the energy transfer associated with a force acting through a distance. (1)功量也是传递中的能量 Work is also energy in transition. We can have push-pull work (e.g. in a piston-cylinder, lifting a weight), electric and magnetic work (e.g. an electric motor), chemical work, surface tension work, elastic work, a rotating shaft. (2)功量是有方向的量 Work is also directional quantity. (
It is stipulated work done by a system is positive, + That is, energy leaves the system.(系统作功,功为 正,也即能量离开系统。 work done on a system is negative That is, energy added to the system,(外界对系统 作功,功为负,即能量加入系统。) (In defining work, we focus on the effects that the system(e.g. an engine) has on its surroundings
It is stipulated: work done by a system is positive, ‘+’. That is, energy leaves the system. ( 系统作功，功为 正，也即能量离开系统。 work done on a system is negative, ‘-’. That is, energy added to the system, （外界对系统 作功，功为负，即能量加入系统。） (In defining work, we focus on the effects that the system (e.g. an engine) has on its surroundings
(3)热量和功量的相似之处) Similarities between heat and work 热量和功量是系统与外界能量交换的机理。 Heat and work are energy transfer surroundings. 功量和热量都要穿越边界 Both heat and work are boundary phenomena. 系统具有能量,但不是功量或热量 System possess energy but not heat or work
(3)热量和功量的相似之处） Similarities between heat and work （ ⚫ 热量和功量是系统与外界能量交换的机理。 Heat and work are energy transfer mechanisms between a system and its surroundings. ⚫ 功量和热量都要穿越边界。 Both heat and work are boundary phenomena. ⚫ 系统具有能量，但不是功量或热量 System possess energy, but not heat or work
两者都是过程量,而不是状态量 Both are associated with a process not a state Both are path functions,(两者都是路径的函数) If the change in a function is dependent on the route taken then the function is known as a path function Example Work vs, heat transfer-- which is which? Can have one the other or both? It depends on what crosses the system boundary. For example consider a resistor that is heating a volume of water
Example. Work vs. heat transfer -- which is which? Can have one, the other, or both? It depends on what crosses the system boundary. For example consider a resistor that is heating a volume of water. 两者都是过程量，而不是状态量 Both are associated with a process, not a state. Both are path functions.（两者都是路径的函数） If the change in a function is dependent on the route taken, then the function is known as a path function