‘J' is mechanical equivalent of heat a conversion factor between two different units of energy: calorie to the joule.

Given

Heat given to system =2625cal =2625×J J

Change in internal energy= 5000J

From graph

V_a=0.02m³

V_b=V_c=0.05m³

P_a=P_b=200kPa=200×10³Pa

P_c=300kPa=300×10³Pa

We know that work done by the gas is given as

ΔW=PΔV

Work done in process abc=ΔW=W_ab+W_bc

ΔW=P_a(V_b-V_a)+0 (∵ W_bc=0 because V_b=V_c)

ΔW=200×10³×(0.05-0.02)=6000J

From first law of thermodynamics, we know that,

ΔQ=ΔU+ΔW

Where ΔQ=heat supplied to the system

ΔU=change in internal energy

ΔW=work done by the system

ΔQ=5000+6000=11000J

But ΔQ=2625cal =2625×J J

Therefore,

2625×J=11000

∴ value of ‘J’ is 4.19joule/cal.