3. The history of electric kettles .
• By the 19th century, kettle makers switched from iron to copper because it
conducted heat more efficiently.
• The next significant improvement – the so-called "whistling kettle" – came
along in the early 20th century and represented a major step in the evolution
of the kettle.
• The first kettle to use electricity to heat water came from Carpenter Electric
Company in Chicago in 1891. However, the water took more than 10
minutes to come to a boil because of a major design problem – the heating
element was in a separate compartment, rather than in the water as is the
case in modern kettles.
• Arthur Leslie Large is credited with inventing the electric kettle .
4. Operation
• Here's how an electric kettle works: Electricity moves through an
element of high resistance, which generates heat that it transfers to
the water.
• At the moment the temperature of the liquid reaches 100 degrees
Celsius, its boiling point, the resulting steam warms a strip
composed of two dissimilar kinds of metal, which curves due to the
fact one of the metals expands more rapidly.
• The heating connection is then broken, preventing electricity from
reaching the element, effectively shutting off the kettle.
• Such a safety feature prevents the scalding water from becoming a
hazard if the person tending it becomes distracted and neglects the
steaming appliance. The "cut-out" device represents a significant
advantage over whistling kettles, which keep boiling, and whistling,
until someone turns down the heat.
