Question

Which of the following expressions represents the first law of thermodynamics?

• A. $q=\Delta E-W$
• B. $\Delta E=q-W$
• C. $\Delta E=q+W$
• D. $\Delta E=q+pdV$

Answer 1

Answer: (B)

Consider a system in a state $A$, having internal energy $E_N,q$ amount of heat is supplied to system so that the system attains the state $B$, having internal energy $E_B$.
Let $W$ is the work done by the system to attain this change, then from first law of thermodynamics.
If $\Delta E=E_B-E_A$ then $\Delta E=q-W$