Ohm's law experiment

To determine the resistance per cm of a given wire by plotting a graph of potential difference versus current, and hence to determine its resistivity.

Real Lab Procedure:

First we'll draw the circuit diagram.

Clean the ends of the connecting wires with sand paper to remove insulation.

Make neat, clean and tight connections according to the circuit diagrams.

Determine the least count of voltmeter and ammeter, and also note the zero error, if any.

          

Real Lab Procedure contd.

Adjust the sliding contact of the rheostat such that a small current passes through the resistance coil or the resistance wire.

Note down the value of the potential difference V from the voltmeter and current I from the ammeter.Shift the rheostat contact slightly so that both the ammeter and voltmeter show full divisions readings and not in fraction.

Record the readings of the voltmeter and ammeter.Take at least six sets of independent observations.Record the observations in a tabular column.

Real Lab Procedure contd.

Now, cut the resistance wire at the points where it leaves the terminals, stretch it and find its length by the meter scale.

Then find out the diameter and hence the radius of the wire using the screw gauge and calculate the cross- sectional area A (πr²).

Plot a graph between current (I) along X-axis and potential difference across the wire (V) along Y-axis.

The graph should be a straight line. Determine the slope of the graph.

 The slope will give the value of resistance (R) of the material of the wire.

Calculate the resistance per centimeter of the wire.

Now,calculate the resistivity of the material of the wire using the formula,                                                                                                  

V versus I graph

A straight line passing through the origin.

Calculation of resistivity

Open Ended

Write your readings for V and I (atleast 6) by performing experiment

Open Ended

Write the value of R and resistivity which you got after doing the calculation.