In supplying $400$ calories of heat to a system,the work done will be

In a thermodynamic process,$200 \ J$ of heat is given to a gas and $100 \ J$ of work is also done on it. The change in internal energy of the gas is ........ $J$.

$A$ perfect gas goes from state $A$ to another state $B$ by absorbing $8 \times 10^5 \ J$ of heat and doing $6.5 \times 10^5 \ J$ of external work. It is now transferred between the same two states in another process in which it absorbs $10^5 \ J$ of heat. Then in the second process:

Write and explain the first law of thermodynamics.

When a system is taken from state $i$ to state $f$ along the path $iaf$,it is found that $Q = 50 \ cal$ and $W = 20 \ cal$. Along the path $ibf$,$Q = 36 \ cal$. The work done $W$ along the path $ibf$ is ....... $cal$.

$A$ thermodynamic system absorbs $2 \, kcal$ of heat and performs $500 \, J$ of work. The change in its internal energy is ......... $J$.