y the bigger the resistance). Also, long thin putty has more resistance than a short thick one of the same material. Also, Ohm’s law states that for a wire under constant physical conditions, the current is proportional to the voltage. This is also equivalent to stating that resistance is constant. If the current through a conductor is I when the voltage across it is V, its resistance R is defined by R= V / I.Resistance (R) is measured in Ohms (Ω).The ohm is the resistance of a conductor in which the current is 1 ampere when a voltage of 1 volt is applied across it. Metals and some alloys give I-V graphs, which are a straight line through the origin, so long as their resistance is constant. Current (I) is directly proportional to Voltage (V) for example, I V. Doubling V doubles I etc. Such conductors obey Ohm’s Law, stated as follows:The current through a metallic conductor is directly proportional to the voltage across its ends if the temperature and other conditions are constant.These are called ohmic or liner conductors and since I V, it follows that V / I = constant. The resistance of an ohmic conductor therefore does not change when the voltage does.Method:Diagram:The equipment needed consists of: Key: Ordinary wires Switch putty A power pack Ammeter variable resistor ammeter Voltmeter 2 crocodile clips battery cell putty 2 one penny coins ...
