Question

A thing about "Conservation of energy...?"

Now we know that energy is always conserved in a "isolated system" over time.
In a non-isolated system, would energy be non-conserved and changing over time?

Could someone give me examples of an isolated system and a non-isolated system?

Thanks
Hope,

Answer 1

Like to invite a dear friend over this @TuringTest . Would you join this matter please? :)

Answer 2

Yea I just realized there aren't any non-isolated system that comes to mind... I doubt there are any "non isolated". Are there?

Answer 3

i can give example of thermos
its is an isolated system your tea stays hot after long time. . .
on other hand you pour tea in a steal glass
its non isolated system so the energy ion form of heat would leak through conductor to environment and enregy of system will lower down by the time. . .(tea will get colder as time passes by)

Answer 4

Interesting.

Answer 5

That's right. In Thermodynamics, you call a system in which energy can be exchanged with the environment "open" and a system that can exchange energy with its surroundings "isolated". Practically, it is difficult to construct a truly closed system (due to radiation, I would argue impossible) but many systems, like a thermos, or some other thermally isolated container, can be approximated as such.

Answer 6

Surely the universe is a completely radiation-tight closed system?

Answer 7

If we're characterizing systems by if and how they interact with their outside environments, I dunno how you'd go about classifying one that has no outside environment to interact with or not. Sure, I guess so...

Answer 8

Are the two laws(Thermodynamics, Conservation) theories? Or based laws? I mean could this laws be studied more and researched more?

Answer 9

Thermodynamics is statistical in nature and is fundamentally based in the behavior of large numbers, and Energy Conservation is a result of the invariance of physics to displacements in time (i.e. the experiment will turn out the same, all other things being equal, if you perform it today or tomorrow), but there's always room to research and more fully comprehend all areas of physics.

Answer 10

Thanks all!

Answer 11

@Jemurray3, one more thing!
Is conservation of energy a law or a theory? What are other "laws" known in physics?

Answer 12

If they are laws. What gives certain theories to become laws? When proven over time and it can not be changed? I don't understand that point.

Answer 13

It's a question of semantics. When a theory has been validated over and over and over and over again with absolutely no known exceptions you might elevate it to the status of law but what we call the thing doesn't really matter. Most would consider the conservation of energy a law, and, for example, the laws of thermodynamics.

Answer 14

But people throw around the term law all the time, like Kirchoff's law, Gauss' law, and Faraday's law in electrodynamics, or Newton's law of gravitation in mechanics.