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# Factors Affecting The Resistance Of A Wire

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Introduction

Page  of

Factors Affecting The Resistance Of A Wire

### Introduction

In this investigation I am going to be looking at which factors may affect the resistance of a wire. A current will be passed through a given wire of a pre-determined length.  For an electric current to flow, there has to be a source of electrons i.e. a battery. Electrons are released from the negative battery terminal (-), and attracted by the positive terminal (+) through the circuit. The resistance of the circuit will limit the amount of electrons moving through it.

The direction of current flow can be considered in two ways, either as conventional current where the flow is from positive to negative or as electron flow from negative to positive. Both are valid. In simple d.c. circuits then conventional current is appropriate. However if an electric field is applied to some free electrons in a copper wire, the electrons start moving, and a current is established. So perhaps it seems that the current should continue forever. After all, a force has been applied, and by Newton's first law (in the absence of friction or other forces, a body in motion will remain in motion), the electrons should keep going.

Middle

V = I x R, This formula would give the voltage.

This formula can then be rearranged so that it gives resistance, this formula is…

It all depends on what you are trying to work out.

### Apparatus I will use

In this experiment I am going to be using many different pieces of equipment, here is a list of all the items I plan to use during my experiment.

• 1 Ammeter
• 1 Voltmeter
• 1 Power Pack (Transformer)
• 1 Un-insinuated, Wire (just over 1 meter long) (approximately # different types)
• 2 Crocodile clips
• 1 Meter Rule

As you can see there is more than one type of wire, this is because it is the only variable I will use in this experiment at the moment; this means that it will be the only thing that will change in the experiment. This is to make the experiment fair and it will also allow me to do the experiment easier because there is only one thing that needs changing.

How to put the apparatus together

1. Connect the power pack to the mains. Making sure that the power pack is turned of at the power switch.
2. Take 2 wires and connect them to the negative and positive terminals of the D.C. power supply.

Conclusion

Nichrome, 28SWG, Diameter 0.375mm

1. One metre length of 0.375mm diameter “Nichrome” (a metal alloy) wire is fixed to the metre rule.

2. The first crocodile clip is clipped to the wire at the 0cm position on the metre rule.

3. The second crocodile clip is clipped to the cable at 10cm intervals of the one-meter length of the given cable.

4. The voltage and current are then read off the ammeter and voltmeter, and recorded at each of these 10cm intervals.

5. The power supply is then turned off allowing the cable to cool down before continuing with next interval on the cable.

(The power passing through the circuit has to be less than 5v, this is because the resistance in the wire causes heat, and if the voltage is too high it will melt the wire.)

RESULTS FOR THE CHANGING THE LENGTH OF THE CABLE

 Length (m) 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 Current (A) 1.02 0.67 0.56 0.42 0.32 0.31 0.28 0.26 0.24 0.23 Voltage (V) 1.34 1.66 1.93 2.05 2.13 2.24 2.37 2.41 2.48 2.57 Resistance (Ω) 1.31 2.48 3.45 4.88 6.66 7.23 8.46 9.27 10.33 10.74 Expected Resistance using the formula above Resistance (Ω) 0.98 1.97 2.95 3.94 4.92 5.91 6.89 7.88 8.86 9.85 % ERROR 33.06 25.95 16.81 23.92 35.29 22.39 22.75 17.69 16.58 9.09

To work out the percentage error (how far away from the expected resistance) I divided the value  I got by the value I expected and multiplied by 100.

As you can see my predictions were within 40% accurate.

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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