How does a pressure cooker work?
A pressure cooker raises the boiling temperature of water by allowing pressure to build inside a sealed vessel.
Why water can exceed 100 °C
At normal atmospheric pressure, water boils near 100 °C at sea level. In a sealed cooker, steam raises internal pressure, so boiling requires a higher temperature.
Why food cooks faster
Water and steam can become hotter than in an open saucepan. Heat transfer and many cooking reactions therefore proceed faster.
The role of the valve
The valve limits pressure by releasing steam once the operating pressure is reached. It regulates the cooker rather than making it perfectly sealed.
Pressure and altitude
At altitude, lower atmospheric pressure lowers the boiling point of water. A pressure cooker partly offsets this by operating above outside pressure.
What to notice in real use
Real devices are never ideal. Response time, insulation, sensor placement, seals, manufacturing tolerances and calibration all affect what you observe. Two appliances based on the same physical principle can therefore behave differently.
That is useful rather than confusing: once the core mechanism is understood, the remaining differences often come from engineering choices rather than from a different law of physics.
Look at the mechanism, not just the object
A useful way to understand an everyday object is to follow a chain: what enters the system, which material or component responds, what physical or chemical change occurs, and what useful effect comes out. This separates the scientific principle from the casing and design.
The same principle often appears in very different objects. Once the mechanism is recognised, links between chemistry, materials, electricity, heat and mechanics become much easier to see.