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# What Factors Affect Resistance.

Extracts from this document...

Introduction

Hashpal .s. Sihre 10.07

WHAT FACTORS AFFECT RESISTANCE

Aim: To investigate how the Factor WIRE LENGH, affects resistance.

Apparatus

Ac Power Pack

100cm of Nickel chrome wire ( swg = 36  )

Ammeter

Voltmeter

Connecters (with negligible resistance)

Scissors

Crocodile clips

Diagram

Predictions

I predict that as the length of the nickel chrome wire decreases, the resistance will decrease as well. This is because the electrons in the current collide with the particles in the wire. The longer the wire the more the particles in it so more collisions are made, so therefore resistance must be higher. When the wire is shorter, there are lees collisions so the resistance smaller

I also believe that the rate at which the resistance of the wire increases will be directly proportional to the length. The graph to show this should therefore look something like this:

Method

The experiment should be set up as in the diagram shown. The power pack should be operated as AC (alternating current, not DC (direct Current) The ammeter must be placed in series to the circuit while the voltmeter must be placed connected in parallel with the resistance wire.

Importantly, the resistance wire must not loop eitherwise it will short circuit, decreasing the resistance value (as current will take the shorter path with less resistance) bending may also affect the resistance in the wire.

Measurements should be taken at regular intervals of 10cm, starting with 10 cm and ending with 100cm. It will be taken as accurately as possible     ( to 1 dp if necessary)

Middle

Before I chose my resistance wire, I took some preliminary results to find out the wire with the highest resistance. As the higher the resistance is, the more accurate I can measure it. I chose 3 materials, copper, nickel chrome and constantan. I took the following swg numbers, 22, 26, 30, 34 and 36. I used a multimeter to find the resistance. Here are my results. (in ohms)

 SWG 22 26 30 34 36 Copper 0.2 0.4 0.5 0.8 1.4 Constantan 0.6 0.8 1.4 2.5 4.3 Nickel chrome 1.3 2 3.2 5.8 7.9

I chose the Nickel chrome wire with a swg of 36 as this gave me the highest resistance. This gave the highest resistance because nickel chrome was more resistant and also it was the thinnest so there was less room for the electrons (in the electricity) to move through so there were more collisions and therefore a higher resistance.

OBSERVATIONS

Table

 Length cm P.D (V) 1 I (A) 1 Resistance (V/I) 1 P.D 2 I 2 R2 P.D 3 I 3

Conclusion

reliability as the line was straight and all the points, (with maybe the exception of the last point) were on our near the line.

From my experiment, I didn’t find any anomalies. I had a thought about a result (highlighted in the table) but this seemed to be reasonably accurate and didn’t make a big difference at all.

My experiment was accurate and very well put together, only minor improvements could have been made. The only suggestions I have is to put  either;

1. A variable resistor in, to control the voltage as the wire got hot as the current went over 0.6 amperes.
2. Or I could have used a multimeter to measure resistance but I would have to subtract resistance in the connecting wires and it might not have been as accurate as the v/I method.

It was also difficult to keep the wire straight and cut exactly 10cm off. I managed to do it very accurately but it was time consuming. But all the wires were kept straight during the experiment. Nether the less these are only minor improvements which would only make the results slightly more accurate and wouldn’t change the conclusion gathered, that resistance increased as the length of wire increased.

The evidence collected was very reliable as it supported both the conclusion made and my prediction. There were no major anomalies to disrupt the evidence collected so it was very reliable (confirmed by graph). I was very happy with my findings.

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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