39. Electrical resistivity is the electrical resistance of a specific specimen of the material of unit length and unit cross- sectional area. The electrical resistivity shows the current opposing property of a conductor. The table shows four different materials and their resistivity. Material Resistivity Material 1 1.62 * 10 ^ 4 Material 2 100 *10^ Material 3 6.84 * 10 ^ 4 Material 4 44 * 10 ^ 4 (a) Name the material, which is the best conductor of electricity? (b) What is the SI unit of resistivity? (c) Why is nichrome wire used in many electrical heating devices? Give two reasons. OR (c) Name the element, which can be used for electrical transmission lines. Give reason. 1 1 2 2