# Resistance of a Wire

Essay by Yourmumma April 2004

A. Planning

Plan of the method to be used: -

The resistivity of nichrome can be determined using the equation ??=?RA/L

Where:

R:- Is the resistance of the wire in ?"ohms" and can be determined using the equation R=V/I where "V" is voltage in volts and "I" is current in

amperes.

L:- Is the length of the nichrome wire used in metres.

A:- Is the cross-sectional area of the wire in metres square and can be determined using the equation A= ??d2 where "d" is the diameter of the wire.

If I plot a graph of length on the x-axis against resistance on the y-axis. From the relation R = ? L /A which corresponds to the st. line equation ?

y=mx the graph should be a st. line passing through the origin where "m" is the gradient of the st. line graph and corresponds to ?/A. Since the cross-sectional area of the wire can be found by knowing itÃÂ´s diameter.

Therefore the resistivity of nichrome can be calculated.

?

Diagram of the circuit used in this experiment

List of the apparatus used: -

1- Power pack supply of 4V

2-A variable resistor

3-A full scale deflection ammeter with a measuring range of 0-1 A

4-A digital voltmeter with a measuring range of 0-5 V

5-P, Q represents terminal blocks.

6-Circuit wires

7-PQ=Nichrome wire

8-A meter ruler

9-Michrometer screw-gauge

10-Sellotape

Detailed method: -

I set up the circuit as shown in the diagram that I have drawn. I started the experiment by taping a meter ruler between the terminal blocks P, Q so that I could measure 100cm of nichrome wire. I made sure that the wire was carefully tightened at both terminals to try to minimise the kinks or twists in the wire. I then switched on the...