Factors affecting the resistance of a wire

Factors affecting the resistance of a wire

Introduction:

Resistance is a force, which opposes the flow of an electric current around a circuit.

Resistance is measured in Ohms. George Ohm discovered that a circuit sometimes resists the flow of electricity. He called this 'RESISTANCE.' He even came up with a rule for working out the resistance of a circuit, which was:

R= V ÷ I

V- Volts

I- Current

R- Resistance

Ohms law says the more resistance means more energy is needed for the current to pass through the wire. Resistance is a measure of how much energy is needed to push the current through something.

Resistance occurs when the electrons travelling along the wire collide with the atoms of the wire. These collisions slow down the flow of electrons causing resistance.

THE FOUR FACTORS THAT AFFECT THE RESISTNCE OF A WIRE ARE:

1. LENGTH OF WIRE

2. THICKNESS OF WIRE

3. TEMPERATURE

4. TYPE OF METAL

AIM:

To investigate how the length of a Nichrome wire can affect the resistance of a wire

PREDICTION:

In my opinion the longer the wire the more resistance there will be. I believe this because if the length of the wire is increased then the resistance will also increase, as the electrons will have a longer distance to travel and so more collision and friction will occur.

VARIABLE FACTORS:

The factors that I am going to vary are the length of the Nichrome wire and adjust the variable resistor to take 3 readings.

The factors that I am going to keep constant are: same thickness of the wire and the set up of the circuit should be the same.

APPARATUS:

v NICHROME WIRE

v POWER PACK

v METER RULER

v CROCODILE CLIPS

v SELLOTAPE

v CONNECTION LEADS

v AMMETER

v VOLTMETER

v VARIABLE RESISTOR

DIAGRAM:

A V

METHOD:

I started of with the experiment by setting up the circuit as shown above. I had to be careful in connecting the circuit, because the voltmeter had to be placed in parallel and the ammeter, which had to be placed in series. The Nichrome wire was cut to just over 100cm so the crocodile clips could attach onto the wire, making the results more accurate. I stretched out the wire and sellotaped it to the ruler. I did this so I do not need to cut the wire every time; all I have to do is just move one of the crocodile clips to another length. The power supply is then switched on and put on 8 volts. I will then record the reading of the ammeter and put the results in a table. After this I will adjust the variable resistor to 7 volts, which would show up on the voltmeter, I will record the reading of the ammeter. I will once again adjust the variable resistor to 6 volts this time and record the reading.

I will repeat this for the other four lengths, which are as follows:

80cm

60cm

40cm

20cm

SAFETY:

The safety precautions that I need to be taken into consideration are: Handle the power supply carefully. Be careful when touching the wire, it may be hot, it might even burn if the voltage exceeds above 8 volts. Do not carry out the experiment in wet areas, as waster is a very good conductor of electricity, which could be dangerous if it comes in contact with the current.

FAIR TESTING:

To ensure that I conduct a fair test I will ensure that the experiment is done at least twice to have more reliable and accurate results. Wire measurements are kept the same and the equipment is in a good working order. I will also ensure that the thickness of the wire stays constant for each length and current. I shall also ensure that the current passing through the wire will not change until all the lengths of wire have been tested and the voltages recorded, then I will increase/decrease the current to the desired voltage. After every time I experiment I will let the wire cool down before I start my other experiment.

Observations:

I will observe the resistance of the circuit and the current, the voltage and ohms. I will also observe the thickness has any effect on resistance and length.

The will also observe the temperature to make sure the heating effect does not change any readings.

Obtaining Evidence

LENGTH(CM) VOLTAGE AMPS RESISTANCE(OHMS)

100 876 0.60.520.49 13.333313.461512.35590

AVERAGE 13.05023

80 876 0.70620.57 11.428511.290310.5263

AVERAGE 11.0817

60 876 0.950.830.74 8.42108.43378.1081

AVERAGE 8.3209

40 876 1.41.21.08 5.71425.83335.5555

AVERAGE 5.701

20 876 2.72.392 2.96292.92883

AVERAGE 2.9639

My prediction was conclusive with my results. It showed that as you increase the length of the Nichrome wire you also increase the amount of resistance. The current is dependent on the amount of voltage, which is applied. The current has to go through a circuit, which contains resistance so if you increase that push you also increase the flow of the current.

CONSLUSION:

The graph is a straight line through the origin, which means Resistance, is roughly proportional to the Length.

This is because if you double length, you double the number of atoms in the wire, so doubling the number of electron, which causes resistance: The results support my predictions well, the results turned out the way I had expected, they match the predicted line well. I had predicted that if you increase the length then resistance will also increase.

So, this effectively means that if the wire was trebled or quadrupled then the resistance would also treble or quadruple.

EVALUATION:

From my graph I can see that my results that I collected are very reliable. I know this because my graph does not show any individual anomalous results. I can see on the graph that none of the results plotted are anomalous because all the points lie fairly along the same straight line.

When I was measuring the lengths of the Nichrome wire, my measurements might have been slightly inaccurate as the rulers used might not have been exact, and it was difficult to get an accurate reading of length by eye, as the wire was not completely straight.

I think that I could have made my experiment more accurate I could use a new or higher quality digital voltmeter.

I also found that the experiment was quite easy to set up, as it was simple and uncomplicated.

Further experiments I could do related to the resistance in a wire, would be to see whether the following factors would make a difference in the resistance of a wire : ( I have made a prediction for each factor from my own scientific knowledge on how I think the resistance would change in a wire for that particular factor )

Thickness of wire:

I think that if the thickness of the wire is increased the resistance will decrease. This is because of the increase in the space for the electrons to travel through. Due to this increased space between the atoms there should be less collisions.

Temperature:

I think that if the wire is heated up the atoms in the wire will start to vibrate because of their increase in energy. This causes more collisions between the electrons and the atoms as the atoms are moving into the path of the electrons. This increase in collisions means that there will be an increase in resistance.

Type of metal:

If the material has a high number of atoms there will be high numbers of electrons causing a lower resistance because of the increase in the number of electrons. Also if the atoms in the material are closely packed then the electrons will have more frequent collisions and the resistance will increase

Jugbir Dhillon