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Resistance of a Wire

Extracts from this document...

Introduction

Background scientific knowledge

Electricity            

Electricity is the movement of charge (electrons) around a circuit. The charge flows throw conductors which allow the electrons to pass through. An object which does not allow electrons to pass through is an insulator.

Conductors intended to have resistance are called resistors (symbol            )image04.png

Voltage- given the symbol V, measured in volts using a voltmeter

Current- given the symbol I, measured in Amperes using an ammeter  

Metallic structure diagramimage05.jpg

image06.png

Resistance

Resistance is the ability to prevent or resist the flow of electrical current. Resistance occurs in an electrical circuit because of a collision between electrons and atoms, which slows the electrons down and converts some of their KE to heat energy. Resistance is measured in Ohms (Ω).


Diagram

Arrow shows direction of electron movement through the wire.

image07.pngimage00.png

Equation

image08.png

Factors which affect resistance

Length of wire – this is being investigated
Thickness of a wire

...read more.

Middle

(I)

(Ω)

Expt. No

Length of

wire

Voltage  

Ave

Current

Ave

Resistance

R=V/I

1

2

3

1

2

3

1

100cm

2

80cm

3

60cm

4

40cm

5

20cm

Graph showing length of wire against resistance

image02.pngimage03.pngimage01.pngimage11.png

Resultstable

(I)

(V)

(Ω)

Expt. No

...read more.

Conclusion

The results support my prediction as there was a bigger resistance in the longer pieces of wire compared to the shorter ones which had a smaller resistance.

Evaluation

The evidence is reliable as I minimised the chance of the wire heating up too much as I used a switch to turn it off when I wasn’t using it. I also took repeats and an average to make sure each result was fairly the same and there weren’t any anomalies.

There were some problems in the procedure as the wire still heated up and the measurement of the wire wasn’t very accurate as there was bends and kinks in the wire.

The improvements I could make are to make sure my measuring of the wire was accurate, to use a longer length of wire and to take more averages.

I couldn’t see any anomalies in my results or on my graph.

The other variables I could investigate arethickness of a wire and material of wire.

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...read more.

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Response to the question

A well set out experiment for this level. The candidate outlines the scientific knowledge of resistance well and relate it to the experiment to get an accurate prediction of what will happen during their experiment and what will be ...

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Response to the question

A well set out experiment for this level. The candidate outlines the scientific knowledge of resistance well and relate it to the experiment to get an accurate prediction of what will happen during their experiment and what will be shown in their results. It is good to back any statement up with valid scientific knowledge as this shows a deeper understanding of the subject and consideration of the experiment and what the results will mean. The candidate makes an accurate evaluation of the experiment but they could include further improvements upon the problems they encountered but this is only an addition as they already provide a good range of possibilities. The conclusion is accurate based on the rest of the experiment.

Level of analysis

The candidate includes a background scientific knowledge section which is really good because it helps the reader understand that the candidate possesses all basic knowledge to make an accurate prediction about the experiment they are carrying out with solid scientific knowledge. Factors which affect resistance and why they do so are outlined well. Factors other than the one being investigated should be kept continuous so they do not bias the experiment. The candidate understands this, hence this is controlled by the candidate which shows a high level of understanding of resistance in this instance. The candidate outlines the method and how he will keep these constant, but one or two of the instructions are hard to interpret so the candidate should make this clearer to ensure the reader knows exactly what they are doing. The prediction of the candidate is good and draws on valid scientific knowledge to make a valid hypothesis.

Quality of writing

In the method punctuation is inconsistent and this should be addressed so the writing does not look 'sloppy.' Otherwise, spelling, grammar and punctuation are to a good standard. The layout of the essay is good with clear subheadings for each different section.


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