I ah 11: Ohm's I aw and Resistivity of Wires Qbjectiye To prove Ohm's Law by plotting a graph of potential difference versus current, and to determine the resistance and resistivity of a wire. Materials Required wire, voltmeter and ammeter, battery, rheostat, one way key, connecting wires According to the Ohm's law, "The current flowing through a conductor is directly proportional to the potential difference across its ends provided the physical conditions (temperature, dimensions, pressure) of the conductor remains the same." If I be the current flowing through a conductor and V be the potential difference across its ends, then according to Ohm's Law: V = RI where, R is the constant Of proportionality. R depends upon the material temperature and dimengnns nt the The potential difference V is measured in volts and the current I in amperes, resistance R is in ohms. To establish the current-voltage relationship, it is to be shown that the ratio V I I remains constant for a given resistance, therefore a graph between the potential difference(V) and the current (l) must be a straight line. For a wire Of uniform cross-section, the resistance depends on the length I and the area of cross-section A. It also depends on the temperature of the conductor. At a given temperature the resistance, 1 where p is the resistivity and is characteristic of the material of wire, L A is the length of the wire, A is the cross-sectional area. Silver Wire, length Of 10 cm, diameter Of .2 mm V&tage (VONS) Rexp = ohms