Question

State and explain the first law of thermodynamics ?

Answer 1

 The first law of thermodynamics is a form of law of conservation of energy applied to

a system. Mathematically it can be written as

$Q=\mathrm{△}U+W$

where Q is heat energy, $\mathrm{△}$U is the change in the internal energy and W is work done.

Q is positive if heat is supplied to the system and negative if it is removed from the

system. $\mathrm{△}$U is positive if there is increase in internal energy and negative if there is

decrease in internal energy of the system. Work done W is positive if work is done

by the system (during expansion) and negative if work is done on the system (during

contraction). The heat energy supplied to a system can be used for increasing its

internal energy and for doing work.