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:

The correct answer is 1 and 3 only.

To understand why the temperature inside a pressure cooker depends on specific factors, let us break down the underlying physics step-by-step:

1. Working Principle of a Pressure Cooker:
A pressure cooker works by trapping steam inside an airtight container. As heat is applied, water evaporates to form steam, which increases the pressure inside the cooker. According to thermodynamic principles, an increase in pressure raises the boiling point of water. Consequently, food cooks faster because it boils at a temperature higher than the standard 100 °C (212 °F).

2. Analysis of the Factors:

Factor 1: Area of the hole in the lid
The pressure inside the cooker is controlled by the vent pipe and the weight placement (whistle). Pressure ($P$) is defined as force per unit area:
$P=\frac{F}{A}$
The area of the hole ($A$) directly affects the internal pressure required to lift the weight. Therefore, the area of the hole plays a crucial role in determining the maximum internal pressure and, subsequently, the cooking temperature.

Factor 2: Temperature of the flame
The temperature of the flame determines the rate at which heat is transferred to the cooker (how fast steam is generated). However, once the operating pressure is reached and steam starts escaping through the vent valve, the internal pressure remains constant. Since the pressure is capped, the boiling temperature inside also remains constant, regardless of whether the flame is set higher or lower (a higher flame only causes steam to release faster).

Factor 3: Weight of the lid (vent weight/whistle)
The downward force ($F$) acting on the hole is determined by the weight of the valve/lid placed over the vent pipe. A heavier weight requires greater steam pressure from inside to lift it and release steam. Since higher pressure results in a higher boiling point, the weight of the lid directly dictates the cooking temperature.

Conclusion:
The temperature at which food cooks inside a pressure cooker depends mainly on the area of the hole in the lid (Factor 1) and the weight of the lid (Factor 3), while the flame temperature only affects the rate of steam formation. Thus, statements 1 and 3 are correct.