Objective 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 Theory 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 dimensions of the conductor. 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 remains constant for a given resistance, therefore a graph between the potential difference(V) and the current (I) 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, R-PA where p is the resistivity and is characteristic of the material of wire, L is the length of the wire, A is the cross-sectional area. Data Case 1: Silver Wire, length of 10 cm, diameter of .2 mm Current (amps) Voltage (volts)Pexp =_ ohms.m %Errorp = % ErrorR2 = (Show work) (Show work) (Show work) Case 2: Silver Wire, length of ? cm, diameter of .2 mm Current (amps) Voltage (volts) Rexp = ohms R2 = Pexp = ohms.m %Errorp = %ErrorR2 = (Show work) (Show work) (Show work) Case 3: Silver Wire, length of 10 cm, diameter of ? mm Current (amps) Voltage (volts) Rexp = ohms R2 = Pexp = ohms.m %Errorp = %ErrorR2 = (Show work) (Show work) (Show work) Case 4: ? Wire, length of ? cm, diameter of ? mm Current (amps) Voltage (volts) Rexp = ohms R2 = Pexp = ohms.m %Errorp = %ErrorR2 = (Show work) (Show work) (Show work)