The physics behind electric heaters turning on automatically when the temperature reaches a certain level of cold involves a basic principle of temperature control called a thermostat.
A thermostat is a device that senses the temperature of a system and uses that information to control the operation of a heating or cooling system. In the case of electric heaters, a thermostat is employed to maintain a desired temperature by monitoring the ambient temperature and activating the heater as needed.
Here's a simplified explanation of how it works:
Sensing: The thermostat contains a temperature sensor, typically a bimetallic strip or a thermistor, which undergoes a physical change in response to temperature variations.
Comparison: When the ambient temperature drops below the desired temperature setting, the temperature sensor triggers a switch or a relay inside the thermostat.
Circuit Activation: The switch or relay closure completes an electrical circuit, allowing current to flow to the heating element of the electric heater.
Heating: As current passes through the heating element, electrical energy is converted into heat through the process of Joule heating. The resistance of the heating element generates heat, which warms up the surrounding environment.
Feedback: As the ambient temperature rises, the temperature sensor detects this increase and eventually reaches the desired temperature setting.
Switching Off: Once the desired temperature is reached, the temperature sensor in the thermostat triggers the switch or relay to open, interrupting the electrical circuit and turning off the electric heater.
This process repeats cyclically, as the thermostat continuously monitors the temperature and activates or deactivates the electric heater accordingly.
The underlying physics involve the principles of electrical resistance (Joule heating) and the physical properties of the temperature sensor (e.g., expansion and contraction of bimetallic strips or resistance changes in thermistors) that allow for temperature detection and control.