00:01
Hi, let us consider internal energy of a system.
00:05
The change in internal energy of a system is given as q minus w.
00:10
This expression is different in different conventions.
00:14
However, in the convention which is followed usually in physics, q is heat.
00:23
When the heat is added to the system, q is greater than zero.
00:34
And when heat is taken away, from system q is less than zero.
00:47
Similarly, for w, when work is done by the system, w is greater than 0, and when work is done on the system, then w is less than 0.
01:11
So keeping these sign conventions in mind, let us see when the internal energy of a system can be increased, which means when is a system is delta q greater than zero so let us imagine a rigid box and let us imagine you have some gas particles in there so if you apply heat to this box of gas with a burner then you are supplying heat to the to the system because this is your system and this is your environment so q is greater than zero and no work is being done done here, so w is equal to 0, which means your change in internal energy is q minus w equals q minus 0 equals q and since q is greater than zero, the internal energy is increasing...