Resistance is the property of an element to resist current and to convert this current in another form of energy like heat. A circular wire has a uniform cross-sectional area. The resistance of a substance which has a uniform cross-sectional area is determined by the following four factors.
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1. Material: The material of any particular substance has a unique molecular structure. The number of free electrons and pressure of charge flow is different for each and every substance. So resistance depends on the molecular structure of the material. This property of the substance to resist current is called the resistivity (?). The higher the resistivity, the more the resistance.
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2. Length: The relationship between the length and resistance is proportional. That is the higher the length, the higher the resistance.
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3. Cross-sectional area: There is an inverse proportional relationship among cross-sectional area of the wire and resistance. If the cross-sectional area is high then the resistance will be low.
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4. Temperature: Hot material is more resistive and thus temperature has a proportional relationship with resistance. If the temperature of the circular wire is high then it will show more resistance.
Now let�s write these relationships in a formula:
R = ? x (l / A)
Where,
R is the resistance of the wire, ? is the resistivity, l is the length of the conductor, and A is the cross sectional area of the wire.
Mr. Muhammad Saqib, M.Sc. (PAK), Research Fellow (PAK), a member of IEEE, is a Fulbright Alumnus and earned his Master’s Degree in Electrical and Power Engineering from University Of Engineering And Technology Taxila, PAKISTAN.
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