Question
Why does the cord of an electric heater not glow while the heating element does?
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Answer
The heating element of an electric heater is made of an alloy (such as Nichrome) which has high resistance (partly due to high resistivity) whereas the cord is made of copper metal which has very low resistance (partly due to low resistivity).
$\rightarrow$ Now, the heating element of an electric heater made of Nichrome glows because it becomes redhot due to the large amount of heat (according to $H=I^2 R t$ ) is produced on passing current.
$\rightarrow$ On the other hand, the connecting cord of the electric heater made of copper does not glow because relatively very less (negligible) heat (according to $H=I^2 R t$ ) is produced in it by passing the same current.
$\rightarrow$ Now, the heating element of an electric heater made of Nichrome glows because it becomes redhot due to the large amount of heat (according to $H=I^2 R t$ ) is produced on passing current.
$\rightarrow$ On the other hand, the connecting cord of the electric heater made of copper does not glow because relatively very less (negligible) heat (according to $H=I^2 R t$ ) is produced in it by passing the same current.
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