In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following? 1. Area of the hole in the lid 2. Temperature of the flame 3. Weight of the lid Select the correct answer using the code given below.

Answer: C. Statements 1 (AREA OF HOLE) and 3 (WEIGHT OF LID) determine the cooking temperature inside a pressure cooker; the flame temperature (2) does not. A PRESSURE COOKER cooks food faster than open-vessel boiling because it allows the water inside to be heated to ABOVE 100°C without boiling away — water's boiling point rises with the pressure above it. Inside a sealed cooker, steam pressure pushes against the cooker walls; the safety/pressure regulator valve (weight on top of the steam vent hole) opens when pressure exceeds a threshold, releasing excess steam. WHAT SETS THE STEADY-STATE INTERNAL PRESSURE (and hence the cooking temperature): - The PRESSURE = (Weight of regulator/lid valve) / (Area of the steam hole). - The valve lifts when steam force (pressure x area) equals or exceeds the regulator weight. Statement 1 (AREA OF THE HOLE): CORRECT. The smaller the hole area, the higher the pressure required to lift the regulator weight, so the higher the cooking temperature. Hole area is a direct determinant. Statement 3 (WEIGHT OF THE LID/REGULATOR): CORRECT. The heavier the regulator, the higher the pressure needed to lift it, so the higher the steady-state internal pressure and cooking temperature. (Domestic cookers typically achieve about 1 atm gauge / 2 atm absolute → ~120-125°C inside.) Statement 2 (TEMPERATURE OF FLAME): WRONG. The flame temperature affects the RATE at which heat enters the cooker (how fast pressure builds), but NOT the STEADY-STATE TEMPERATURE inside. Once the regulator opens, the cooker reaches a fixed equilibrium pressure determined by weight/area; excess heat input simply boils off more steam at the same pressure. A hotter flame makes the cooker reach equilibrium faster but does not raise the cooking temperature above the equilibrium value. So 1 and 3 determine the cooking temperature; 2 does not. Source: NCERT Class 11 Physics 'Thermal Properties of Matter' / Engineering thermodynamics texts.