The Resistance of a Wire

The Resistance of a Wire

Introduction

In this investigation I will be trying to find out the resistance of a

piece of constantan wire. I know that according to ohms law, the p.d

is proportional to the current so if the p.d doubles so will the

current. Through past experiments I know how to work out resistance,

to work it out I use this formula

Where the resistance is R, the p.d is V and the current is C, from

this you can work out the resistance of any circuit.

Aim of the Preliminary

The aim of this preliminary work involves making decisions about the

length and thickness of the wire, which will be suitable for the main

investigation

The preliminary work will only involve one type of wire - constantan

because there are available 5 different thicknesses of this wire and

very few of other wires in the department.

The 5 different thicknesses of wire I am testing are

1 36 SWG (very thin)

2 34 SWG

3 30 SWG

4 28 SWG

5 26 SWG (very thick)

I tested all the wires at 3 volts, first I set up the equipment as

shown below (Diagram) and then recording the results on the table

below

Results

SWG Type

Length of wire in mm

Voltage

(volts)

Current

(a)

36

500

3

0.52

34

500

3

0.62

30

500

3

0.81

28

500

3

1.73

26

500

3

2.23

36

400

3

0.63

34

400

3

0.89

30

400

3

1.43

28

400

3

2.13

26

400

3

2.