• 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)

    Sticky tape Fix the wire on the ruler Micrometer screw gauge Measure the diameter of the wire 1. I stuck two wires separately onto two rulers. Make sure both wires started from 0cm then ended at 100cm on the rule.

  2. Peer reviewed

    Investgating resistivity - Planning and Implementing

    4 star(s)

    Resistances are also given to two decimal places, as given the accuracy of the voltage and current the resistance is calculated with, further decimal places could not be supported. Length is measured to the nearest mm, so these values in metres are given to three decimal places.

  1. Physics - Resistivity

    I am going to conduct six repeats, using the power supply's built in electromotive force variables, from 3 to 12 in steps of 1.5. I am going to record, the electromotive force, and the voltage across the bulb, the current around the circuit and the resistance in the bulb.

  2. resistivity if a nichrome wire

    The electrons in the wire gain more kinetic energy causing them to vibrate more. This means that the collision of the electrons increase between the electrons and the ions in the wire. Therefore there is of a less chance that the electrons are being carried across the component.

  1. Measuring The Resistivity Of A Pencil Lead.

    Source of Error The biggest source in the experiment is in the calculating the resistivity. This is due to the fact that one has to square the resistance value.

  2. investigating the relationship between the diameter and the current in a wire at its ...

    Determining a maximum and minimum diameter for the wire I decided to use the maximum and minimum values of wire that were available. These were 14SWG and 32SWG. I decided to use all of the available thicknesses as it would give me a more accurate set result.

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

    Resistance is defined and calculated using the formula: Resistance = voltage � current or R = V � I Ohm's law states that: "The current through a metallic conductor is directly proportional to its voltage provided that temperature is kept constant".

  2. Free essay

    Resistance of a wire

    / I When resistance is measured the unit is given in Ohm's. 1 ohm (?) means 1 Volt is needed across my wire to sustain a 1Amp current, they are all related. PREDICTION Through my own knowledge gained I know that as the lengths of the wire increases so will resistivity.

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