The reason you have to hold down the gas button for a few seconds when lighting a stove or gas oven is to allow the thermocouple to heat up and generate a small electric current. The thermocouple is a safety device designed to prevent gas leaks and potential accidents.
Here's how it works:
Pilot Light: In many gas stoves and ovens, there is a small, continuous flame called a pilot light. The pilot light is a gas flame that is always burning, even when the stove or oven is not in use. It serves as a source of ignition for the main burner.
Thermocouple: The thermocouple is a heat-sensitive device located near the pilot light. It consists of two different metals joined together. When the pilot light is lit, the heat from the flame causes the thermocouple to generate a small electric current.
Safety Mechanism: The electric current produced by the heated thermocouple keeps a valve open, allowing gas to flow to the pilot light and the main burner. As long as the thermocouple detects the presence of the pilot light's flame, the valve remains open, and the gas supply to the burner is maintained. However, if the pilot light goes out, the thermocouple quickly cools down, and the electric current stops.
Holding the Gas Button: When you press and hold the gas button while lighting the stove or oven, you are allowing gas to flow to the pilot light. Simultaneously, you are also heating up the thermocouple. After a few seconds, the thermocouple generates enough current to keep the gas valve open even after you release the gas button. This ensures that the pilot light remains lit and continues to provide ignition for the main burner.
Safety Shutdown: If, for any reason, the pilot light goes out (e.g., a draft or malfunction), the thermocouple will cool down, the electric current will stop, and the gas valve will close. This safety feature prevents the uncontrolled release of gas into your home, reducing the risk of gas leaks and potential hazards.
By following the correct procedure and holding the gas button for a few seconds when lighting the stove or oven, you ensure that the thermocouple is heated sufficiently to keep the gas supply regulated and your appliance operating safely.