The conservation of energy
Energy can be transferred from one form to another, but it cannot be created or destroyed.
The Principle of Conservation of Energy states that: energy can be changed from one form to another but the total amount of energy does not change.
In the diagram above, if 100 J of electrical energy is supplied to the lamp and only 10 J is transferred to the surroundings as useful light energy, then the remaining, 90 J (100 J 鈥 10 J), is transferred to the surroundings as wasted heat energy.
The total amount of energy has not changed, it is still 100 J.
Electrical energy input to the lamp = 100 J.
Heat and light energy output from the lamp = 100 J.
The energy transfer to light energy is the useful transfer.
The rest is 鈥榳asted鈥.
It is transferred to the surroundings, making them warmer.
This 鈥榳asted鈥 energy becomes so spread out that it becomes very difficult to do anything useful with it.