Which wave will generate more heat?

  • Thread starter samieee
  • Start date
  • #1
67
0

Main Question or Discussion Point

Suppose there are some waveforms to be used as current input: i)sine wave ii)square wave iii) triangle wave iv)sawtooth wave and v)sawtooth wave with both the cycles(+ve half cycle and -ve half cycle) in positive Y axis. Which wave will generate more heat?

Actually, I faced this question in a recent examination. Though I ansewered (v), now I think the right answer would be square wave, as it grabs the maximum magnitude for more duration of time than the others. Am I right?

Thanks.
 

Answers and Replies

  • #2
818
67
  • #3
67
0
So, from the comparison, I see that square wave has the higher value than any other rotating wave. DC shifted square wave has even higher value as it should have.
 
  • #4
818
67
So, from the comparison, I see that square wave has the higher value than any other rotating wave. DC shifted square wave has even higher value as it should have.
Right, so your intuition with regards to the square wave was spot on.

The instantaneous power delivered to the resistor is ##p(t) = R i(t)^2##. If you try to imagine the graph of ##p(t)## for your waveforms, it should confirm your idea of why its average value is highest in the case of the square wave.
 
  • #5
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,098
129
Suppose there are some waveforms to be used as current input: i)sine wave ii)square wave iii) triangle wave iv)sawtooth wave and v)sawtooth wave with both the cycles(+ve half cycle and -ve half cycle) in positive Y axis. Which wave will generate more heat?
This question cannot really be answered as stated here. Are the amplitudes of all the waves supposed to be the same? That needs to be specified.
 
  • #6
67
0
Are the amplitudes of all the waves supposed to be the same? That needs to be specified.
Yes, amplitudes of all the waves are same.
 
  • #7
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,098
129
Okay. So yes, it is the square wave. As milesyoung said, you need to consider [itex]i^2 R[/itex].
 
  • #8
1,354
336
Also assuming the loads are the same.
 
  • #9
KHMOU YOUSSEF
All the signals have the same frequency?
 
  • #10
Redbelly98
Staff Emeritus
Science Advisor
Homework Helper
Insights Author
12,098
129
Also assuming the loads are the same.
Yes.

All the signals have the same frequency?
That does not matter. The average of i2 is the same no matter what the frequency is. Just for example, for a sine wave, it is (1/2) the square of the amplitude, independent of the frequency.
 
  • #11
204
3
The real question is could you make a saw tooth laser beam if you super imposed different frequencies on top of each other. Not sure how this could be accomplished but its an interesting thought.
 
  • #12
1,354
336
Huh? Lasers operate at one frequency, i.e perfect sine wave oscillation, unless you mean to modulate the laser?
 
  • #13
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,071
Suppose there are some waveforms to be used as current input: i)sine wave ii)square wave iii) triangle wave iv)sawtooth wave and v)sawtooth wave with both the cycles(+ve half cycle and -ve half cycle) in positive Y axis. Which wave will generate more heat?
That's the beauty of the RMS value, it directly relates to the heating value (in a resistive load). :smile:
 
  • #14
NascentOxygen
Staff Emeritus
Science Advisor
9,244
1,071
Huh? Lasers operate at one frequency, i.e perfect sine wave oscillation, unless you mean to modulate the laser?
Wouldn't frequency-doubling lasers allow you to generate some coherent harmonics?
 
  • #15
1,233
17
or you could modulate the injection current to get a sawtooth amplitude at some frequency << lasing frequency
 

Related Threads on Which wave will generate more heat?

Replies
16
Views
1K
Replies
5
Views
416
  • Last Post
Replies
2
Views
859
  • Last Post
Replies
22
Views
8K
  • Last Post
Replies
7
Views
8K
  • Last Post
Replies
2
Views
2K
  • Last Post
Replies
7
Views
7K
  • Last Post
Replies
3
Views
9K
Top