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Resistance Aim: my main aim is to investigate the factors that affect the resistance in a conductor, in which here I am using a nichrome wire.

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Introduction

What factors affect the resistance of wire?

Aim: my main aim is to investigate the factors that affect the resistance in a conductor, in which here I am using a nichrome wire. The focal factors that affect the resistance in a conductor are:

• Length
• Temperature
• Cross- section area
• Material

Hypothesis: I think that the more the cross-section area, the lower the resistance in the conductor or the nichrome wire will be. This is because the resistance happen due to the movement of the electrons through the material ( once a voltage has been applied ) they collide with the atoms in the material and as a result lose some of their energy. The idea of resistance is simply how difficult it is for the electrons to move through a material. The more difficult it is, the more energy they lose in the material on their movements.

The definition of an electrical resistance is the ratio of voltage to current. The equation we use to find the resistance from the current and voltage is:

Resistance (R) = Voltage (V) / Current (I)

To put it in a simpler way, it is the number of volts difference across the object when one amp of current flows. It should be remembered that voltage is the number of joules of energy transferred by one coulomb of charge, and that current is the number of coulombs of charge passing a place each second.

Now what the object is made of this means its resistance will have an affect on its resistance. Not all metals are equally as good at conducting electricity. A longer length of wire will also make it difficult for the current to flow, as there is more material to travel through.

The temperature too plays a great role in the affect of the metallic conductor’s resistance.

Middle

0.50

4

8.29

72.40

73.00

71.80

0.60

5

8.29

84.40

84.40

84.40

0.70

6

8.32

96.10

95.90

96.30

0.80

7

8.29

108.60

108.60

108.60

0.90

8

Average =  8.30

Material: Nichrome Wire                    Length: 75cm                   Thickness: 0.45mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 6.50 30.75 31.20 30.30 0.20 1 6.51 46.05 46.10 46.00 0.30 2 6.54 61.20 61.60 60.80 0.40 3 6.49 77.05 77.10 77.00 0.50 4 6.47 92.75 92.40 93.10 0.60 5 6.46 108.35 108.20 108.50 0.70 6 6.50 123.15 122.70 123.60 0.80 7 6.47 139.00 139.20 138.80 0.90 8 Average = 6.49

Material:Nichrome Wire                 Length: 50cm                   Thickness: 0.45mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 4.15 24.10 25.00 23.20 0.10 1 4.02 49.70 49.90 49.50 0.20 2 4.07 73.65 73.60 73.70 0.30 3 4.08 98.15 98.30 98.00 0.40 4 4.07 122.75 122.80 122.70 0.50 5 4.05 148.20 148.30 148.10 0.60 6 4.09 171.05 171.20 170.90 0.70 7 4.08 195.95 196.00 195.90 0.80 8 Average =  4.08

Material: Nichrome Wire                 Length: 25cm                   Thickness: 0.45mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 2.27 22.00 22.50 21.50 0.05 1 2.48 24.15 24.50 23.80 0.06 2 2.39 29.35 29.90 28.80 0.07 3 2.43 32.95 33.20 32.70 0.08 4 2.41 37.35 38.00 36.70 0.09 5 2.40 41.60 42.20 41.00 0.10 6 2.34 47.00 47.60 46.40 0.11 7 2.34 51.30 51.90 50.70 0.12 8 Average =  2.38

Resistance from graph

Lengths:

100cm

= 24.00/0.20

= 120

Resistance = 1/120 = 0.0083 x 1000

= 8.33

75cm

= 30.75/0.20

= 153.75

Resistance = 1/153.75 = 0.0065 x 1000

= 6.50

50cm

= 24.10/0.10

= 241

Resistance = 1/241 = 0.00414 x 1000

= 4.14

25cm

= 22.00/0.05

= 440

Resistance = 1/440 = 0.00227 x 1000

= 2.27

Different Thickness

Material: Nichrome Wire                 Length: 100cm                   Thickness: 0.90mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 2.37 42.20 42.20 42.20 0.10 1 2.30 65.30 65.10 65.50 0.15 2 2.31 86.50 86.60 86.40 0.20 3 2.32 107.60 107.50 107.70 0.25 4 2.35 127.75 127.80 127.70 0.30 5 2.34 149.60 149.60 149.60 0.35 6 2.32 172.65 172.60 172.70 0.40 7 8 Average =   2.33

Material: Nichrome Wire                 Length: 100cm                   Thickness: 0.45mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 8.46 23.65 23.50 23.80 0.20 1 8.29 30.15 30.10 30.20 0.25 2 8.34 35.95 36.20 35.70 0.30 3 8.43 41.50 41.40 41.60 0.35 4 8.43 47.45 47.00 47.90 0.40 5 8.35 53.90 53.80 54.00 0.45 6 8.47 59.00 59.00 59.00 0.50 7 8 Average  = 8.40

Material: Nichrome Wire                 Length: 100cm                   Thickness: 0.56mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 4.92 40.68 40.65 40.70 0.20 1 4.89 51.18 51.35 51.00 0.25 2 4.87 61.63 61.95 61.30 0.30 3 4.80 72.85 73.10 72.60 0.35 4 4.84 82.58 82.85 82.30 0.40 5 4.85 92.78 92.95 92.60 0.45 6 4.82 103.83 103.95 103.70 0.50 7 8 Average =  4.86

Material: Nichrome Wire                 Length: 100cm                   Thickness: 0.32mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 8.85 22.60 22.70 22.50 0.20 1 8.70 28.75 28.80 28.70 0.25 2 8.67 34.60 34.80 34.40 0.30 3 8.75 40.00 40.30 39.70 0.35 4 8.71 45.90 45.70 46.10 0.40 5 8.69 51.80 51.60 52.00 0.45 6 8.77 57.00 57.00 57.00 0.50 7 8 Average  =  8.73

Resistance from graph

Thickness:

0.90mm

= 42.20/0.10

= 422

Resistance = 1/422 = 0.00236 x 1000

= 2.36

0.45mm

= 23.65/0.20

=118.25

Resistance = 1/118.25 = 0.00845 x 1000

= 8.45

0.56mm

= 40.68/0.20

= 203.4

Resistance = 1/203.4 = 0.00491 x 1000

= 4.91

0.32mm

= 22.60/0.20

= 113

Resistance = 1/113 = 0.00884 x 1000

= 8.84

Series    Material: Nichrome Wire           Length: 100cm and 75cm              Thickness: 0.45mm

 mA Resistance (Ω) Average Current (mA) Current (decreasing in voltage) Current (increasing voltage) Voltage (V) Sly. No 15.90 25.15 25.10 25.20 0.40 1 15.85 31.55 31.50 31.60 0.50 2 15.98 37.55 37.30 37.80 0.60 3 16.00 43.75 43.60 43.90 0.70 4 15.90 50.30 50.30 50.30 0.80 5 15.92 56.55 56.50 56.60 0.90 6 15.99 62.55 62.40 62.70 1.00 7 15.92 69.10 69.10 69.10 1.10 8 Average  =   15.93

Conclusion

b Use the variable power supply and the variable resistor to vary the potential difference across the lamp, from 1.0 V to 10.0 V in intervals of 1 volt. Record pairs of potential difference and current values in the table.

You can record results for currents in the opposite direction by reversing the connections on the lamp.

c. Plot a graph of current/A (y-axis) against potential difference/V (x-axis).

The resistance of the lamp at a particular potential difference = potential difference/current.
.

Hypothesis

1 The aim of this experiment is to develop confidence in setting up simple circuits and in taking careful measurements.

2 It is often stated that the resistance of a component is the gradient of a V against I graph. This is not necessarily the case.

3 In the case of a filament lamp it is, in fact, the resistance that increases (rather than the number of charge carriers falling) due to increased lattice vibrations. For a filament lamp, however, the temperature of the filament is most definitely not constant (it must to get hot in order to give out light!)

The resistance of a lamp's filament (the long, thin, coiled wire) increases dramatically as the current increases. This results in the following graph:     Diodes

For diodes, only tiny currents of a few micro amps (millionths of an amp) flow at low voltages. Putting more than about 1.5 volts across them normally makes them "turn on" allowing current to flow.

This gives rise to a rather curious-looking graph of current against voltage   One special thing about diodes is that if you connect them the "wrong way around" in a circuit, they have a very high resistance, so virtually no current flows (less than a micro amp).

This means a better graph of their behaviour includes a large zero section:     Of course, if you put too high a voltage across them, even the "wrong way", they will blow up as too much current flows!

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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3 star(s)

Although there is a large amount of detail in this report there is also some confusion in its structure.
1. Have one section for each aspect of the investigation and include all of the relevant information within it; this will remove the need to repeat information several times.
2. The investigation loses focus. For each of the tests there should only be one independent investigation.
3. The significance of the R value is not explained fully.
4. The evaluation is the strongest section.
***

Marked by teacher Luke Smithen 05/09/2013

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