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# Ohm's Law Investigation

Extracts from this document...

Introduction

Safety

-Don’t overheat nicrome wire, use very low current to prevent wire breaking

-Place all schoolbags under tables

-Place stools under table

Background Knowledge

The flow of electricity along a wire is similar to the flow of water along a pipe.  For more water to flow down the pipe, you have to push the water harder by turning the tap.  This is the same in electric circuits.  More current flows along a wire when the EMF pushing the electrons is greater.  Ohm’s law describes how the current and the voltage flowing a wire are related. Electrical resistance is a property of all materials.  It measures how much the material inhibits the flow of electrons.  High resistance allows a small amount of current to flow.  This resistance is measured in ohms (   ).  Nicrome wire opposes the flow of current more than copper, therefore nicrome has a higher resistance than copper.  Non-metals insulate electricity, therefore they have a high resistance, whereas metals conduct electricity so they have a low resistance.

Middle

46

80

0.1

8

80

0.2

18

80

0.4

34

Trend

From my results, I noticed the following trend.

As I double the length of the nicrome wire, I double the resistance.  This is very obvious from my table of results.

 Length(Cm) Voltage(V) Current(mA) Current(A) Resistance=V Average resistance 30 0.1 22 0.022 4.5 30 0.2 46 0.046 4.4 30 0.4 92 0.092 4.3 4 60 0.1 12 0.012 8.3 60 0.2 24 0.024 8.3 60 0.4 46 0.046 9 9 80 0.1 8 0.008 12.5 80 0.2 18 0.018 11.1 80 0.4 34 0.034 11.8 12

These results clearly show now as we double the resistance we double the resistance and as we treble the length, we treble the resistance.

E.g.  A length of 30cm=resistance of 3

A length of 60cm=resistance of 8

From this you can see that the resistance did double, but I have an anonymous result at 60cm, as it did not double exactly , this could have been caused by a human error, refer to the analysis of results for more detail on this.

3d Diagram

The following is a 3d diagram of the experiment in which I conducted to find the resistance of a piece of nicrome wire.

Circuit diagram

The following is a circuit diagram of the experiment in which I conducted.

Analysis of results.

Now having carried out the experiment, and got accurate results.

Conclusion

My results, from conducting the experiment were fairly accurate a I repeated the experiment three times for each different length of nichrome wire.

If I were to repeat the experiment again I would take more results so I would be sure that my results were reliable, make sure at all times that the nichrome wire was perfectly straight, or could measure the temperature of the nichrome wire by putting it into a water bath, as when I was conducting the experiment I just assumed the temperature at room temperature.

Graph

Now having completed my graph showing length of nichrome wire via average resistance, I found it supports my earlier prediction as there is a straight line through the origin and the length of the nichrome wire is directly proportional to the resistance of the wire.

As you can see from graph I have drawn in different color lines to prove my prediction is correct.

I.e. Length=30  Average Resistance=4

Length=60 Average Resistance=9

This student written piece of work is one of many that can be found in our GCSE Electricity and Magnetism section.

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