QUICK HOMEWORK HELP! What's the difference between a positive and negative feedback loop?
If you're able to can you please provide an example of each?
- GeronimoLv 74 years ago
An example of negative feedback is in the operation of a toilet bowl tank. When the tank
is empty water rushes in. The float rises and provides the mechanical negative feedback
to slowly close the water input valve. The higher the float rises the less water enters the
An example of positive feedback occurs when a microphone gets too close to the speaker
that it ultimately drives and the electronic gain of the amplifiers is set too high. The system
becomes unstable when any small input to the microphone causes a speaker output that is
detected by the microphone as an even bigger input signal; and that in turn creates a bigger
speaker output which creates an even bigger microphone signal and so on. The system
quickly generates that loud screeching sound we are all familiar with.
- Ms. WorthLv 74 years ago
In positive feedback, the more the system changes, the more of that change occurs. The effect increases itself constantly.
Example: It is known that the sight of frightened people running away causes watching people to panic and start running away too.
So if a couple of people start running away, then some of the people seeing that will start to run away too.
Now there are a few additional people running away, and so even more people see people running away, so then they feel panic and start to run away too.
Now a lot of people are running away, and they infect even more people with the panicky urge to run away ... and on and on until almost everyone is running away in a panic.
Positive feed back loops lead to less stability in the system because they keep on magnifying the consequences.
In a negative feedback loop, an increase in some input causes the system to dampen down the response.
Example: It is known that the ticket sales to a new movie depend heavily on the enjoyment of friends who have already seen it.
When the movie opens on its first weekend, the more the first viewers hated it, the fewer new tickets will be sold.
The fewer tickets that are sold, the fewer reports of "enjoyment" will be heard, and when the number of people who hated it increases, fewer and fewer tickets will be sold.
Negative feedback loops tend to increase stability in a system.
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