How many joules are equivalent to 500 cal of heat? (1 cal = 4.186 J )
**Cyclic work** equals area inside loop, for rectangular cycle P₁V₁→P₂V₁→P₂V₂→P₁V₂→P₁V₁, W = (P₂-P₁)(V₂-V₁), heat absorbed and rejected during different legs, net work output for heat engine, input for refrigerator. Heat in J = Heat in cal × 4.186 . 500 × 4.186 = 2093 J . Using first law ΔU = Q - W, W = ∫ P dV, isobaric W = P ΔV, isothermal W = n R T ln(V₂/V₁), adiabatic P V^γ = const and η = 1 - T_c/T_h, evaluation yields 2093 J, consistent with thermodynamic laws and energy conservation.
Ref: NCERT > Physics Book > Thermodynamics > Cyclic Processes and Reversibility Concepts