How many calories are equivalent to 1674 J of heat? (1 cal = 4.186 J )
**Modes of energy transfer** work is force times displacement, e.g., gas expansion W = P ΔV, heat is due to temperature gradient, internal energy change same for different combinations of Q and W, e.g., same ΔU can be achieved by adding heat at constant volume or doing work adiabatically, illustrating equivalence but distinction in mechanism. Heat in cal = Heat in J4.186 . (1674)/(4.186) ≈ 399.9 ≈ 400 cal . 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 -
Ref: NCERT > Physics Book > Thermodynamics > Work Heat Distinction and Energy Transfer Modes