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Question

Why are the conductors of electric heating devices like toasters and irons composed of an alloy rather than a pure metal?


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Solution

Heating effect of current:

  1. When we use some electrical appliances, the chemical processes that take place inside the cells on which they run generate some potential difference between its terminals and sets the electrons in motion.
  2. The source must release part of its stored energy in order to keep the current flowing. In the case of electrically powered fans, for example, a portion of the energy is used to move the fan blades.
  3. The leftover energy is used or expanded as heat, which raises the appliance's temperature. When using a circuit in an appliance that is solely resistive, a significant amount of energy is completely lost as heat. This is referred to as the heating effect of current.
  4. When an electric current is passed through a conductor, it generates heat due to the hindrance caused by the conductor to the flowing current. The work done in overcoming the hindrance to the current generates heat in that conductor.

Applications of heating effect of current:

1. In an electric heater, high resistance nichrome wire is used as a coil. The coil is wound on grooves made up of ceramic material or china clay. When the current flows in the coil, it becomes heated, which is then used to heat cooking vessels.

2. Mica is an insulator that is placed between the alloy part and the coil in an iron. The coil becomes heated with the passage of current which is then transferred to the metallic part through mica. Finally, the metal part becomes heated which is then used for ironing clothes.

Explanation:

The conductors of electric heating devices such as bread toasters and electric irons are made of alloy because the resistivity of an alloy is more than that of metals which produces a large amount of heat. Some of the characteristics of the alloy are as follows:

  1. At high temperatures, the alloys do not oxidize.
  2. Alloy does not melt readily and gets deformed.
  3. Alloys have a low-temperature coefficient of resistance.
  4. Alloys do not corrode easily.

Hence, alloys are used in electric heating devices, such as bread-toasters and electric irons The conductor of electric heating devices is manufactured of an alloy rather than pure metal for pure metal melts quickly when heated and corrodes readily.


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