Resistance Of A Wire Essay, Research Paper

I am conducting

this experiment to determine how a certain variable affects the resistance of a

piece of wire in a circuit. PLANNINGSafety To make the experiment safe I will: ·

Make sure the wire is not connected for long periods of

time. This makes the wire hot and destroys equipment. ·

Disconnect the wires should the ammeter reading go too

high.PredictionI predict that as the length of wire increases the

resistance will increase. This is because the electrons have further to travel

and lose energy. Equipment·

Power supply (0 ? 10v) ·

Ammeter (0 ? 5 Amps) ·

Digital voltmeter ·

Crocodile clips (x3) ·

Meter ruler ·

Nichrome wire (I metre) ·

Leads/connectors (x7) ·

Variable resistor Possible Variables ·

Length of wire ·

Voltage ·

Temperature of wire ·

Current flowing through wire ·

Width of wire ·

Type of wire (copper, steel etc) ·

Equipment in use (leads rheostat)To make the experiment a fair test I will vary only one

thing- the length of the wire. The current and voltage stay the same. The wire

will stay the same except for length. I will use nichrome wire in my circuit.I am going to measure the voltage from 10 cm to 100 cm in

10 cm increments. I will repeat the experiment 3 times in order to gain an

average result and use Ohm?s law to calculate the resistance.RESULTS TABLE Length

of wire 1 Voltage 2 3 Average

volts (V) Resistance R=V/I (W) 0 0 0 0 0 0 10 0.35 0.33 0.35 0.34 0.17 20 0.65 0.65 0.66 0.65 0.33 30 0.99 0.98 0.97 0.98 0.49 40 1.3 1.4 1.3 1.3 0.65 50 1.66 1.65 1.67 1.66 0.83 60 1.98 1.98 1.99 1.98 0.99 70 2.29 2.29 2.27 2.28 1.14 80 2.65 2.64 2.65 2.65 1.33 90 2.97 2.95 2.96 2.96 1.48 100 3.28 3.29 3.30 3.29 1.65 ANALYSIS AND CONCLUSIONSFrom my graph I can see that the straight line indicates

that the length of the wire is proportional to the resistance.As the length of the wire was increased the resistance

also increases. This is because the current is made up of electrons. The

electrons lose energy the further they have to travel. Also, as the wire gets

hotter, the resistance increases because the atoms in the wire vibrate more and

this makes it difficult for the electrons to pass through the wire.I can now say that my prediction ?as the length of the

wire increases the resistance will increase? is supported by my results. EVALUATION I obtained my results by setting up the circuit show in

the diagram on the previous page. I moved the crocodile clips in 10 cm

increments and read the voltage off the digital voltmeter. I repeated the

experiment twice more and then calculated an average voltage. I then calculated

the resistance by dividing the current (2 amps) by the average voltage. This

method of calculating resistance is known as Ohm?s Law.From my graph, I can see that my results were accurate.

All the points are very close or on the line of best fit in a positive

correlation. There were no anomalous results.?As I obtained

accurate results, I think that the method I used was suitable. However, there are certain improvements I could make to

improve the accuracy, namely:·

Making sure the wire is straight so measurements could be

taken accurately. ·

Making the wire straight would enable more accurate

positioning of the crocodile clips, which again would give more accurate

results. ·

Letting the wire cool down sufficiently in between

readings. When the wire heats up, it has lots of energy, which causes the atoms

in it to vibrate, making it harder for the electrons to travel. This increases

the resistance via another method, so it is not a truly fair test.?As I have

previously stated, my results have a good standard of accuracy. This is shown

by the points being near or on the line of best fit and there were no anomalous

results. Therefore my results support a firm conclusion that the length of wire

is proportional to the resistance.