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The table below lists the melting points of a few metals & alloys. Based on this table identify which material will be most suitable to be used in making the following electrical appliances? Name of the metal Melting point in °C Copper 1084 Brass 930 Lead 328 Nichrome 1150 Lead & Tin 200 Aluminium 660 Berylium Copper 865-955

The table below lists the melting points of a few metals & alloys. Based on this table identify which material will be most suitable to be used in making the following electrical appliances? Name of the metal Melting point in °C Copper 1084 Brass 930 Lead 328 Nichrome 1150 Lead & Tin 200 Aluminium 660 Berylium Copper 865-955 Correct Answer <span style="">Room heater element - Nichrome, Fuse wire - Lead &amp; Tin</span>

The correct answer is Room heater element - Nichrome, Fuse wire - Lead & Tin.

Concept:

  • Heating elements in electric appliances work on the principle of Joule's law of heating. When a current passes through a material, the material heats up, according to the law. This is due to the given resistance of the material.
  • The ability of a material to oppose the flow of charges when a potential difference is applied across the material is referred to as resistance.
  • The rate of heat produced with time (power of heat) in the material is given by P=i2R.
  • This means that the heat generated in a conducting material is proportional to the resistance of the material.
  • Specific resistance is the resistance of the material for one unit length and one unit cross sectional area.

Explanation:

  • Nichrome is a metal used to make the heating elements of electrical appliances. 
  • Because of its high melting point and high resistivity (low conductivity), nichrome wire is used as a heating element.
  • When a large amount of heat is produced, the nichrome wire does not melt easily due to its high melting point.
  • The resistivity of a material is directly proportional to its resistance.
  • Resistivity of the material is reciprocal of its conductivity. 
  • Nichrome has a high resistivity and a low conductivity.
  • Nichrome wire is used as a heating element because it has high specific resistance.
  • Fuse wire is made of tin and lead alloy because of its high resistance and low melting point
  • A fuse wire is made of tin alloy because it has a low melting point and will melt easily when a short circuit occurs, whereas copper wire cannot be used as a fuse wire because it has a high melting point and will not melt easily when a short circuit occurs.

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