Question

Three processes completes a thermodynamic cycle for an ideal gas as shown in the $P-V$ diagram . Find the processes in correct sequential order.

• A. $1\to 2$ Isothermal expansion
  $2\to 3$ Isochoric process
  $3\to 1$ Adiabatic expansion
• B. $1\to 2$ Isothermal expansion
  $2\to 3$ Isochoric process
  $3\to 1$ Adiabatic compression
• C. $1\to 2$ Adiabatic compression
  $2\to 3$ Isochoric process
  $3\to 1$ Isothermal compression
• D. $1\to 2$ Isothermal expansion
  $2\to 3$ Isochoric process
  $3\to 1$ Isothermal compression

Answer 1

The correct option is B $1\to 2$ Isothermal expansion

$2\to 3$ Isochoric process
$3\to 1$ Adiabatic compression
From indicator diagram,
$(1\to 2)$ must be an isothermal expansion, during which temperature of the system remains constant but volume is increased.

From figure $(2\to 3)$ is an isochoric process, as the volume remains constant during process.

$(3\to 1)$ and $(1\to 2)$ both follow hyperbolic profile on the $P-V$ curve, since curve for process $(3\to 1)$ has a higher slope ( being more steep). Hence $3\to 1$ is an adiabatic compression.