Question

Change in internal energy =heat + work done this explains law of energy conservation , how ?

Answer 1

Hi!

I'd prefer explaining this with an example.

Consider a hair dryer that you use to dry your hair after shower. When you plug it into the switch board and start using, you see that there is hot air coming out that makes your hair dry. This is the work done by the dryer.

Also, after you are done, you notice that the dryer is now hot to touch. This is the energy lost as heat.

So, no system in this universe is perfect. No machine can utilise all of the energy supplied to perform work. Some energy is lost to the surrounding environment.

Hence, the statement :

Internal energy (in this case, energy in the hair dryer) = work done(drying your hair) + heat (the machine turns hot. You can touch and feel)

Now, it should be easy for you to understand why it can be explained via the law of conservation of energy. This is because, Law of conservation of energy states that: # Energy is neither created nor destroyed. It simply changes from one form to another.

The energy that is supplied via the switch board into the dryer is now converted into work for drying hair and lost as heat.

If you measure the heat lost and the work done. Then, add both the values, you will see that the total is equal to the energy provided through switch board.