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The conservation of energy says that it can neither be created nor be destroyed, it can only be transferred from one form to another. i had this doubt in my mind for a long time that why do we need to save energy if the total energy is conserved. Energy can never be destroyed so why do we need to save energy?

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    $\begingroup$ Consider doing an online search to find existing answers such as this one. $\endgroup$ Aug 25, 2023 at 18:31
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    $\begingroup$ Usable form of energy at our control is important. This is what need to be saved. $\endgroup$
    – Shafeek
    Aug 25, 2023 at 18:31
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    $\begingroup$ Veritasium has a video that covers this: youtube.com/watch?v=DxL2HoqLbyA $\endgroup$
    – md2perpe
    Aug 25, 2023 at 18:58

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Energy cannot be created nor destroyed. However, in many cases (such as ones where they talk of "conserving energy") energy can be stored in many forms, some of which are more useful than others. As a trite example, the energy in your gas tank, stored as chemical energy, can be harnessed to get you to the store. Or we can set fire to all of the gasoline in an uncontrolled manner, converting all of that energy into heat. The amount of energy did not change, but that heat energy is in a form that cannot be leveraged to get you to the store. If you care about getting to the store, you better conserve the energy in your gas tank, so that the engine can carefully convert that energy into a combination of heat and kinetic energy to drive your car forward.

So when we say "save energy," we're really taking about "saving energy that is in a useful form."

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Energy that we need to save is energy stored in forms usable to us - say the energy one can obtain from burning fuel in cars. When we "waste" energy, it means it's being converted into some form of energy unusable to us. Physically, the energy is conserved, but it loses its utility fast.

If you were to just burn the fuel instead of using it to fuel an engine, a lot of heat energy would be produced, which is not useful to us and can be therefore considered as having been "wasted". Think about it. Can we use sound, heat, or light energy practically?

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"Saving energy" in daily life actually means preventing energy from transforming from its very useful forms (e.g. electric energy, gravity energy of water in a dam, or chemical potential energy stored in separated fuel and oxygen) into its less useful forms (e.g. heat, internal energy, thermal radiation).

"Saving energy" is used probably because most people do not regard dissipated energy (heat, internal energy, thermal radiation) as a valuable kind of energy; it is hard to concentrate, utilize, transform into other forms. Except for heating buildings, most of the time, it is not useful, so people tend to use the word "energy" only for the more useful forms, and that's where "saving energy" comes from.

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Energy can't be destroyed, but it is often made less versatile. For example, if we bring a car to rest by applying the brakes, most of the car's original kinetic energy is transferred to internal (thermal) energy in the brake discs and brake pads – they get hot. We can't though, turn very much of this energy back into kinetic energy for the car even if we tried. This is not just because we are limited by technology; we are limited by the Second Law of Thermodynamics! There is overwhelming experimental evidence for this law, as well as a convincing theoretical basis: crudely speaking energy can be too thinly spread for all of it to be converted to a more useful form. 'Saving energy' means refraining from converting energy from a versatile to a non-versatile form.

A quite different reason for 'saving energy' is that using energy from many convenient sources (like fossil fuels, either by direct burning or via electricity) involves the emission of carbon dioxide into the atmosphere.

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You have to consider entropy as well.Entropy in a closed system is either increasing or staying constant.Well if the entropy of a system is staying constant then work is not done in that system.And if the entropy of a system is increasing , energy is being converted from 1 form into another form and the product of this conversion is less useful than what we had at the beginning.

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