Ductility is defined as the ability of the material to deform to a greater extent before the sign of crack, when it is subjected to tensile force. Ductile materials are those materials which deform plastically to a greater extent prior to fracture e.g. mild steel, copper and aluminium.
For Euler’s formula to be applicable the critical stress must not exceed the proportional limit. Now crushing stress in mild steel = 3300 kg/cm2 = 330 N/mm2 But stress at proportional limit in mild steel = 250 M/mm2 Euler’s buckling stress
λ = 88.55 ≈ 89 Thus slenderness ratio should be more than or equal to 89 ideally. Option (d) is the most close one.
Explanation : In Electrolux refrigerator Ammonia evaporates in hydrogen.
The ammonia liquid leaving the condenser enters the evaporator and evaporates into the hydrogen at the low temperature corresponding to its low partial pressure. The mixture of ammonia and hydrogen passes to the absorber into which is also admitted water from the separator. The water absorbs the ammonia and the hydrogen returns to the evaporator. In the absorber the ammonia therefore passes from the ammonia circuit into water circuit as ammonia in water solution. This strong solution passes to the generator where it is heated and the vapor given off rises to the separator. The water with the vapor is separated out and a weak solution of ammonia is passed back to the absorber, thus completing the water circuit. The ammonia vapor rises from the separator to the condenser where it is condensed and then returned to the evaporator.