• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

investigating the relationship between the diameter and the current in a wire at its melting point

Extracts from this document...

Introduction

Investigation Report

Aim –

Theory –

When current is passed through a wire resistance is created. This resistance is depends on the resistivity of the wire, current, voltage, wire length and cross-sectional area.

So…

R = ρ . l

        A

R = Resistance.

Ρ = Resistivity.

L = Length.

A = Cross sectional area.

(Pg. 200, Accessible Physics, 1995, MacMillan Press ,ISBN  0333-627-80-6)

(Pg. 47, Advanced Physics Revision Handbook, 1996, Oxford University Press, ISBN 0-19-914640-3)

Looking for a formula for resistance -  

R = ρ . l        ( Resistance is the product of resistivity and length

         A                       per unit cross sectional area.)

R = Resistance.

Ρ = Resistivity.

L = Length.

A = Cross sectional area.

(http://physics.bu.edu/~duffy/PY106/Resistance.html)

Looking for a formula for voltage –

V = I . R  (Voltage is the product of current and resistance)

V = Voltage

I = Current

R = Resistance

(http://www.allaboutcircuits.com/vol_1/chpt_2/1.html)

Looking for a formula for Cross sectional area –

A = Πr2   (Cross sectional area is the product of pie and radius                                      

                                                squared)

Or. A = Π image03.png2   ( Cross sectional area is the product of pie and

                                        diameter per unit 2 all squared)

A = Cross sectional area

Π = Pie

D = Diameter

(http://www.equationsheet.com/sheets/Equations-20.html)

So putting these formula together-

A = Π image03.png2     And        R = ρ . l

                                                 A        

R =  ρ . l

     Π (d/2)2

R = ρ . l

     Π . d2/4

R = 4 . ρ . l

        Π . d2

R = 4 . ρ . l   .     1

            Π            d2

R           =            4 . ρ . l           .            1                     + 0

                                Π                           d2image00.pngimage00.png

image01.png

          Y          =             m                       x                 +c

References to the specification –

Aim Of My Investigation –

...read more.

Middle

By using a digital ammeter and voltmeter the uncertainties in the measurement will be kept as low as possible. In these cases both uncertainties are about one percent. If the resistance alone was measured the uncertainty would be a lot higher and therefore the results would be of decreased effectiveness.

Determining the additional resistance:

An additional resistance of three ohms will be added to the circuit. This will lower the current to around one amp which will be enough to protect the ammeter and prevent any major heating in the wire that could, potentially, change the resistance. Since it was found that a thin nicrome wire with two amps passing through it was hot enough to glow red, which would affect the resistance significantly, the current needs to be kept to around one amp. This should still provide a good reading on both the ammeter and the voltmeter while removing the problems faced by temperature on all the test wires.

‘The resistance of a metal increases with an increase of temperature’

(Pg. 87 ‘Essential AS Physics for OCR’ By Jim Breithaupt, Nelson Thornes, ISBN 0 7487 8507 8)

image02.png

Ohm meter (Ω) – o-200Ω

Constantan Wire – 30 swg.

Resistance – 3.2 Ωhms.

Some after heat change – Temperature changes of less than 10 oc (i.e. changes in room temperature) have little or no effect on resistance.

Determining the wires material:

...read more.

Conclusion

This can be accounted for by reference to the % uncertainty in my voltage, current, resistance and diameter.

Sources of error –

In my experiment there where several sources of error. Firstly, the diameter of a thinner wire would be more accurate than that of a thicker wire. This is because when they are made they have to be made to a certain percentage accuracy of there thickness, thus a thicker wire will have a bigger margin if error in production. I could improve the accuracy of the diameter of the wire by checking it myself with a micrometer.

Secondly, when measuring out the metre length of wire, the thinner wire will be a more accurate length. This is because the thicker wire is full of kinks and thus is almost impossible to get perfectly straight. One way I could improve the accuracy of measuring the wire is by using sellotape to hold the wire to the meter rule while I measured the wire.

Thirdly, the voltage and current I recorded in my results is particularly accurate. This is because the ammeter and voltmeter is not very accurate. The only way to improve these readings is to use a more accurate ammeter and voltmeter.

Fourthly, I only did one set of results for my experiment. This means I could not take mean results. If I was doing this experiment again I would take multiply results and take a mean of these results.

...read more.

This student written piece of work is one of many that can be found in our AS and A Level Electrical & Thermal Physics section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related AS and A Level Electrical & Thermal Physics essays

  1. Peer reviewed

    Measurement of the resistivity of Nichrome

    5 star(s)

    Act as a variable resistor which value of voltage and current can be taken 2 pairs of crocodile clips Connect wires in the circuit An iron slice Change the length of wire connected in the circuit 2 cells (3V) Work as a power supply An voltmeter Record the voltage. (V)

  2. Free essay

    Resistance of a wire

    experiment will now produce more accurate results, I will ensure this even further by repeating each test 3 times with 30seconds cool down between each test. This will be much more time consuming but will ensure that I get accurate results.

  1. Measuring The Resistivity Of A Pencil Lead.

    This increases the margin of error. The actual value for the biggest source of error is : 0.0595mm Improvements The reliability of the techniques I used are quite reliable but there is still room for improvement. A good way to improve would be to have a pencil lead not in the wooden casing.

  2. Characteristics of Ohmic and Non Ohmic Conductors.

    noted down by checking the reverse such as decreasing the voltage, temperature, etc. * It should be noted whether the connections are positive or negative from the supply to the ammeter and voltmeter. * The ammeter should be connected in series and the voltmeter in parallel.

  1. How different factors affect the resistance of a wire

    Section 4: Evaluating Anomalous results After plotting and drawing a line graph, I could easily recognise the trend and spot a few anomalies as well. It was quite difficult to draw my line of best fit as the last 4 recordings could have sent the line in two different directions.

  2. The varying of the resistance of nichrome wire depending on its length

    The amount of current let through will not vary in any of the tests. However, before conducting the actual investigation I carried out a preliminary investigation in which my aim is to find out how current varies with voltage when using a fixed value resistor and when using a filament lamp.

  1. I am going to investigate what the resistivity is of a pencil lead. ...

    This means that when the voltage is doubled so is the current. For example: 0.4V=0.470A and 0.8V=0.917A. This is almost exact but other factors may have influenced the result such as human error etc. The typical resistivity of many semi conductors is 102 so my result is quite far away

  2. Investigating the effect of 'length' on the resistance of a wire

    DIAGRAM No.2 OF A VOLTMETER CONNECTED IN PARALLEL TO A CIRCUIT IN TWO DIFFERENT POSITIONS. DIAGRAM No.3 OF AN AMMETER CONNECTED IN SERIES TO A CIRCUIT. Resistance is a measure of the opposition to current. The greater the resistance of a wire, the smaller the current that passes for a given voltage.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work