Define resistance and resistivity. Give the relation between them. Explain the dependence of resistance on temperature.

Define resistance and resistivity. Give the relation between them. Explain the dependence of resistance on temperature.

Grade:12th pass

1 Answers

Pawan Prajapati
askIITians Faculty 60785 Points
2 years ago
Hint: First write the definition and properties of Resistance and resistivity properly, describe its units, on which factors it depends. Then write the relation between resistivity and resistance which is actually the formula for resistance in a conductor. Then write the dependence of resistance on temperature. Complete step-by-step answer: Resistance is the property of the conductor which opposes the free flow of electric current or electron. Resistance can also be simplified as the ratio of the voltage applied to the electric current flowing through it. The resistance of a conductor generally depends on a number of factors : length, nature of the material, and the area of cross-section. For a conductor material, the resistance of the material is inversely proportional to the area of cross-section and directly proportional to the length of the conductor. Resistivity is a property of a conductor which is defined as the resistance offered by a material per unit length for a unit cross-section. The SI unit that we use for resistivity is Ohm.meter . Resistivity increases linearly with the increase in temperature. When we compare resistivity of the insulators with the resistivity of the conductor it is pretty low. Therefore, we can represent it as: Resistivity of insulators > Resistivity of alloys > Resistivity of conductors Relation between Resistivity and Resistance is: R=ρlA, where ρ is the resistivity, l is the length of the conductor and A is the cross sectional area. We know that the resistivity of a material depends on the temperature. Resistivity decreases with the decrease in temperature and increases with the increase in temperature. Thus, from the above relation we can say that the resistance of a material also increases or decreases with the increase and decrease in temperature. Note: Do not break the order of the question try to answer in the same order as the question is given. Students generally do mistake in the terms on which resistivity depends like maximum students try to derive it from the resistance in a conductor relation it is where they go wrong.

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