Why are all energy transfers NOT perfect?

Question

homework!!!!!!!!!!!!

Answer 1

In a sense energy transfers must be perfect in that E can't be destroyed, but E can be changed into another form even in part. The form in question is heat. It is said that heat is the dumping ground of the universe. All other energies around the universe will eventually end up as sparsely distributed heat in the end. So, in everyday usage, everything that is done in this world produces heat as some product. Typically, it is waste heat that does no work for you. It is "lost".

Answer 2

The short answer is because there are always inefficiencies.

Consider total energy of a system TE = KE + PE + WE + QE; where KE, PE, and WE are different kinds of energy (e.g., kinetic, potential, work).  QE is lost energy, like in heat losses due to friction for example.

Now efficiency is defined as e = WE/TE; so that if the energy transfer is "perfect" we have e = 1.00 = WE/TE or TE = WE and 100% (perfect) efficiency.  In other words, in a perfect transfer, all the total energy would be converted into work.  

But for this to happen, we need KE = PE = QE = 0 to be true.  That is, if any one of these three other kinds of energy are non-zero, e < 1.00 indicating the energy transfer was not perfect.  And in truth QE > 0 always because there is always friction in any system.  There are always losses.

We can get friction down very very low, especially in labs, but never zero.  So e < 1.00 and that means there is no such thing as a perfect energy transfer and, consequently, there is no such thing as a perpetual motion machine.  That is, to keep a system going, we always have to add more or less energy to it, depending on its efficiency, which is always less than 100%.

Answer 3

The second law of thermodynamics (the entropy law or law of entropy) was formulated in the middle of the last century by Clausius and Thomson following Carnot's earlier observation that, like the fall or flow of a stream that turns a mill wheel, it is the "fall" or flow of heat from higher to lower temperatures that motivates a steam engine. The key insight was that the world is inherently active, and that whenever an energy distribution is out of equilibrium a potential or thermodynamic "force" (the gradient of a potential) exists that the world acts spontaneously to dissipate or minimize. All real-world change or dynamics is seen to follow, or be motivated, by this law. So whereas the first law expresses that which remains the same, or is time-symmetric, in all real-world processes the second law expresses that which changes and motivates the change, the fundamental time-asymmetry, in all real-world process. Clausius coined the term "entropy" to refer to the dissipated potential and the second law, in its most general form, states that the world acts spontaneously to minimize potentials (or equivalently maximize entropy), and with this, active end-directedness or time-asymmetry was, for the first time, given a universal physical basis. The balance equation of the second law, expressed as S > 0, says that in all natural processes the entropy of the world always increases, and thus whereas with the first law there is no time, and the past, present, and future are indistinguishable, the second law, with its one-way flow, introduces the basis for telling the difference.

The active nature of the second law is intuitively easy to grasp and empirically demonstrate. If a glass of hot liquid is placed in a colder room a potential exists and a flow of heat is spontaneously produced from the cup to the room until it is minimized (or the entropy is maximized) at which point the temperatures are the same and all flows stop.

Answer 4

Because some energy gets dissipated to the outer universe in some form as heat or sound. But, if the system was completely seperate  from the universe and the transfer points were completely perect, then yes Energy transfer would be perfect. But, it is a physical impossibility.