The term wasted energy like the sound energy from the hair dryer is wasted energy and thermal energy from using the phone for too long
So if we aren’t benefiting from this Wasted Energy
How this comply with the law of conservation of energy
Where does the sound energy go does it convert to other forms or it disappears
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It gets converted to heat and radiates into space. It’s not “destroyed” in the sense of violating conservation, but turns into an unusable form. *Granted hair dryers produce heat on purpose, but a particular measure of heat generated can only be used once. And of course other appliances are made to generate as little heat as possible because it’s not part of their purpose, so isn’t even used the first time.
Energy is not destroyed, but it can easily become less useful. As a general rule, heat energy is not very useful, although this changes at higher temperatures.
We can’t turn heat energy back into useful energy unless the temperature is high. A few degrees is nothing. Only at a few hundred degrees do we get any real efficiency. Hopefully your phone isn’t getting that hot.
Wasted energy, in the end, becomes thermal. Thermal energy is the energy associated with temperature. It is the energy of random motions of molecules.
The hair dryer and phone get hot, and this heat dissipates into the air, warming it just a little bit. The air particles move just a little bit faster. No energy disappeared, but it becomes less useful, because there is no way of using a warm gas on its own to to useful work.
The energy of sound, the energy of motion, all go to the same place. Sound energy spreads out and becomes less intense until it becomes indistinguishable from the random motions of molecules. When an object stops due to friction, the surfaces along which it experienced friction heats up, and this also dissipates into the air, the ground, and the object.
The term wasted energy means that there was a purpose for the energy and any energy that is used not for that purpose is wasted. You can use energy in the same way for 2 different reasons and the amount of wasted energy changes depending on the reason.
For example some lightbulbs are used for heat, when they are being used for light then the heat is the wasted energy but when they are being used as heaters/warmers then the light is the wasted energy.
So energy is only wasted if it has a purpose.
If your home is too cold or is likely to be too cold soon then the hair dryer sound energy isn’t wasted, since most of it will be converted to heat within the building. Whenever a surface absorbs a sound and doesn’t echo it all back that means the energy was converted to heat.
It’s not really an issue with hair dryers, since the vast majority of the energy will come out as heat in the hot air that we want anyway.
Energy is only useful when concentrated, but at the same time energy naturally seeks to spread out over time. The energy isn’t destroyed, but it *is* functionally lost to us in that it can not longer be used to produce work.
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