The automatic activation of electric heaters based on temperature is typically achieved using a device called a thermostat. Thermostats are designed to sense the ambient temperature and control the operation of heating or cooling systems accordingly. The physics involved in this process can be explained as follows:
Temperature Sensing: Thermostats contain a temperature-sensing element, which is often a bimetallic strip or a thermistor. A bimetallic strip consists of two different metals bonded together that have different rates of expansion when heated. A thermistor is a temperature-sensitive resistor that changes its electrical resistance with temperature. These sensing elements detect changes in temperature and convert them into corresponding changes in their physical properties.
Set Temperature: The thermostat is set to a specific temperature by the user. When the ambient temperature drops below the set temperature, it triggers the activation of the electric heater.
Circuit Control: The thermostat is connected to the electrical circuit that powers the heater. When the ambient temperature falls below the set temperature, the temperature-sensing element of the thermostat undergoes a physical change (e.g., bending of the bimetallic strip or a change in resistance in the thermistor).
Contact Switching: The physical change in the temperature-sensing element causes the thermostat to switch the electrical circuit controlling the heater. In the case of a bimetallic strip, the bending can lead to the opening or closing of an electrical contact. In the case of a thermistor, the change in resistance can trigger electronic circuitry to activate the heater.
Heating Activation: Once the electrical circuit is closed or completed by the thermostat, electric current flows through the heating element of the heater. The heating element converts electrical energy into heat energy through resistive heating, producing warmth in the surroundings.
Temperature Regulation: As the heater operates and emits heat, the ambient temperature gradually rises. Once the temperature reaches or exceeds the set temperature on the thermostat, the physical properties of the temperature-sensing element are altered again, causing the thermostat to open the electrical circuit and deactivate the heater. This cycle continues as the ambient temperature fluctuates around the set temperature.
In summary, the physics involved in the automatic activation of electric heaters based on temperature relies on the principles of temperature sensing, physical property changes in the temperature-sensing element, and the control of electrical circuits to regulate the heating process.