- $\text{W}_{\text{LN}}=\text{PdV}=0$
$\text{W}_{\text{NM}}=\text{P}[\text{V}_\text{M}-\text{V}_\text{M}]=10[6-2]=40\text{J}$
$\text{W}_\text{LMN}=\text{W}_{\text{NM}}=0+40=40\text{J}$
Along LM WLM = Area under the curve LM
= Area of $\Delta\text{LMQ}+$ Area of rectangle LQZP.
$=\frac12\times\text{LQ}\times\text{MQ}+\text{LP}\times\text{PZ}$
$=\frac12\times4\times5+5\times4$
$=10+20=30\text{J}$
So work done is less along LM.
- $\text{U}_\text{L}=20\text{J}$
$\Delta\text{Q}=400\text{J}$
$\text{dQ}=\text{dU}+\text{dW}$
$=(\text{U}_\text{M}-\text{U}_\text{L})+\Delta\text{W}_{\text{LM}}$
$\text{U}_\text{M}=\text{dQ}+\text{U}_\text{L}-\Delta\text{W}_\text{LM}$
$=400+20-30$
$=390\text{J}$
