Important Questions on Electricity
Give an expression for the resistivity of a substance along with their symbols and units. 
What happens to the resistance with respect to the area of cross-section? Give reason: "The heating elements of electrical heating appliances are made up of alloys rather than a pure metal". Compare the resistivity of conductors, semiconductors and insulators with respect to temperature. What does the term "the resistivity of copper is " refer to? Which has a high value of resistivity: A long copper wire or a long copper wire? What is the SI unit of resistivity? What are the factors on which resistivity depends? 
