Solved Problem -2 · Part 2

hence the passage of current through it. It is different for different materials . From Ohm’s Law, = R. The resistance of a conductor can be defined as the ratio between the potential difference across the ends of the conductor and the current flowing through it . . . Unit of Resistance The SI unit of resistance is ohm and it is represented by the symbol Ω. th Standard Science Resistance of a conductor is said to be one ohm if a current of one ampere flows through it when a potential difference of one volt is maintained across its ends . ohm = Solved Problem- Calculate the resistance of a conductor through which a current of A passes, when the potential difference between its ends is V. Solution: Current through the conductor I = A, Potential Difference V = V From Ohm’s Law: R = . Therefore, R = = Ω . ELECTRICAL RESISTIVITY & ELECTRICAL CONDUCTIVITY . . Electrical Resistivity You can verify by doing an experiment that the resistance of any conductor ‘R’ is directly proportional to the length of the conductor ‘L’ and is inversely proportional to its area of cross section ‘A’. R L, R , Hence , R Therefore, R = ρ ( . ) Where, ρ (rho) is a constant, called as electrical resistivity or specific resistance of the material of the conductor. From equation ( . ), ρ = If L = m, A = m then, from the above equation ρ = R Hence, the electrical resistivity of a material is defined as the resistance of a conductor of unit length and unit area of cross section . Its unit is ohm metre . Electrical resistivity of a conductor is a measure of the resisting power of a specified material to the passage of an electric current. It is a constant for a given material. Nichrome is a conductor with highest resistivity equal to . × – Ω m. Hence, it is used in making heating elements. . . Conductance and