Question

Based on the first law of thermodynamics, which one of the following is correct?
A. For an isochoric process, $E = - Q$
B. For an adiabatic process, $E = - Q$
C. For an isothermal process, $E = - Q$
D. For a cyclic process, $W = - Q$

Answer 1

We need to remember that in thermodynamics, internal energy is defined as the energy associated with a substance. Internal energy is commonly denoted by the symbol $U$ or $E$ , the net heat transferred into the system is denoted by the symbol $Q$, $Q$ is that the sum of all transfer into and out of the system, and work is done by the system or done on the system is denoted by $W$ .

Complete step by step answer:
We must know that the method of operation which may bring out a change within the system is named thermodynamic process. A thermodynamic process is often administered in several ways and different conditions.
As we know that the law of conservation of energy, the total energy remains constant when changes from one form to another is known as the first law of thermodynamics.
Mathematically,
$\Delta U = q + w$
Isochoric process: The volume of the system remains constant in an isochoric process.
$\Delta V = 0$
$\therefore$ $w = p\Delta V = 0$ , $\Delta E = Q$
Adiabatic process: No heat flow into or out of the system is called adiabatic process.
For an adiabatic process, $Q = 0$. So, $\Delta E = W$ .
Isothermal process: During the change from initial to final state, temperature of the system remains constant.
For an isothermal process, $dT = 0$.
Cyclic process: After completing a series of changes, the system returns to its original state and is said that a cycle is complete. This is called a cyclic process.
For a cyclic process,$\Delta U = 0,\Delta H = 0,\Delta P = 0,\Delta V = 0$ And $\Delta T = 0$. As the internal energy $U$so during a process net change of internal energy will be equal to zero, $\Delta U = 0$. So, $W = - Q$.
For a cyclic process, $W = - Q$ is the correct answer.

So, the correct answer is Option D.

Note: We need to remember that the universe may be split into two parts, part of the universe chosen for thermodynamic consideration is called a system. The thermodynamic consideration in the system is to study the effect of pressure, temperature, etc.