100% efficiency?

  • #1
(ok i not sure where this topic goes so ill take a guess its here)

ok, I hear that nothing is 100% efficienct. some energy is always lost as heat and sound. however, what about heating elements? or electrical heats or whatever, surely the lost heat (and i dont think any sound cause its electrical) isn't really lost because it can be thought of as part of the output?

can anyone explain to me where I am flawed. thnx
 

Answers and Replies

  • #2
Andrew Mason
Science Advisor
Homework Helper
7,656
383
(ok i not sure where this topic goes so ill take a guess its here)

ok, I hear that nothing is 100% efficienct. some energy is always lost as heat and sound. however, what about heating elements? or electrical heats or whatever, surely the lost heat (and i dont think any sound cause its electrical) isn't really lost because it can be thought of as part of the output?

can anyone explain to me where I am flawed. thnx
Efficiency is measured by Work out/Energy in . Heat is not work. Work + heat always amounts to 100% of the energy.

AM
 
  • #3
o rite, well my text book (only 16yearold level lol) says efficiency was useful energy out/energy in

am i right in saying they have used a simpler version for my level then?
 
  • #4
ranger
Gold Member
1,676
1
o rite, well my text book (only 16yearold level lol) says efficiency was useful energy out/energy in

am i right in saying they have used a simpler version for my level then?
Think of (useful)Energy out/Energy in as a ratio that describes the efficiency. Where the highest quotient you can get is 1. You can convert it to a percentage, just multiply it by 100. So if all energy in went to its intended purpose (all energy in was useful work), we have 1*100 = 100% efficiency.
 
  • #5
russ_watters
Mentor
20,286
6,865
I'm fine with seeing a heating element as 100% efficient, but if it makes you feel better, you lose some in the wires too...
 
  • #7
BillJx
Or you could look at a heating element as being (almost) 100% inefficient. Your lightbulb does useful work in lighting your room, and incidental work in heating it. The incidental work is called inefficiency in the same way that an unwanted plant is called a weed.

Now, here's the joke. Well meaning people will run out in the middle of winter to replace all their filament bulbs with more "efficient" mini-flourescents, and their baseboard heaters replace the energy they "saved".

The same point could be made about the winter energy costs of your refrigerator, computer, etc. A watt is a watt is a watt.

Efficiency refers to a value that we put on things. All of the energy is used; what percentage is used for something we want?

The reason I suggest that a heating element is 100% inefficient, is that it converts the energy directly to its lowest state. In principle, we could heat our houses with the "waste" heat from other processes.
 
  • #8
78
1
(ok i not sure where this topic goes so ill take a guess its here)

ok, I hear that nothing is 100% efficienct. some energy is always lost as heat and sound. however, what about heating elements? or electrical heats or whatever, surely the lost heat (and i dont think any sound cause its electrical) isn't really lost because it can be thought of as part of the output?

can anyone explain to me where I am flawed. thnx
A heating element will output light (EM radiation in general) in frequencies that won't be absorbed by the material in the room to increase its temprature - you can see it as energy loss.
 
  • #9
863
4
The reason I suggest that a heating element is 100% inefficient, is that it converts the energy directly to its lowest state. In principle, we could heat our houses with the "waste" heat from other processes.
I agree - I would say in general converting energy to a state of more disorder is "inefficient".
 

Related Threads on 100% efficiency?

  • Last Post
Replies
9
Views
5K
  • Last Post
Replies
11
Views
12K
Replies
4
Views
992
Replies
2
Views
17K
  • Last Post
Replies
3
Views
634
  • Last Post
Replies
7
Views
6K
  • Last Post
Replies
3
Views
2K
  • Last Post
Replies
1
Views
7K
  • Last Post
Replies
5
Views
3K
  • Last Post
Replies
8
Views
1K
Top