Mar. 18, 2025
Every morning, we brush our teeth, wash our faces, and then boil a pot of hot water—especially in winter, a warm cup of water feels incredibly comforting. In modern life, electric kettles have become an essential household appliance. With just a few minutes of heating, they provide hot water for tea, coffee, instant noodles, and more.
You may have noticed a convenient feature: when the water reaches boiling temperature, the kettle automatically turns off. This means we don’t have to keep an eye on it, making it both safe and hassle-free. But how exactly does this work? The answer lies in an electronic component called a thermistor.
Thermistor: The "Temperature Sensor" of an Electric Kettle
A thermistor is a special electronic component that is highly sensitive to temperature changes. Its resistance value changes as the temperature fluctuates. You can think of it as the kettle’s temperature detector, continuously monitoring the water temperature and sending information to the control circuit.
The thermistor plays several key roles:
Temperature Measurement – It detects temperature changes by measuring resistance, just like a thermometer.
Temperature Compensation – It helps ensure that other electronic components are not affected by temperature fluctuations.
Overcurrent Protection – Certain types of thermistors, such as PTC (Positive Temperature Coefficient) thermistors, can quickly increase their resistance when excessive current flows, thereby limiting the current and preventing circuit damage.
How Does an Electric Kettle Automatically Shut Off?
The heating process in an electric kettle is actually a temperature control system at work:
When powered on, the heating element starts warming up the water.
As the temperature approaches 100°C, steam affects the kettle’s sensing components, such as the bimetallic thermostat or thermistor.
The thermistor detects the high temperature, causing its resistance to change, which sends a signal to the control circuit.
The control circuit recognizes that the preset temperature has been reached and cuts off the power supply, stopping the heating process.
You can think of this as an "automatic doorman": when the water is fully boiled, the thermistor essentially "alerts" the control circuit, which immediately "presses the switch" to stop the kettle from heating further.
This article is provided by JYH HSU (JEC) Electronics. JEC is a research, development, production, and sales-oriented company specializing in manufacturing and selling various electronic components such as capacitors and resistors.
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