Wire Resistance Investigation
Wire Resistance Investigation
Aim:
To investigate how the length of a wire can affect resistance.
Safety:
My main concern will be that if I turn the voltage up to high the wire could snap and hot metal could fly up into the eye. So I will wear goggles to protect my eyes.
Method:
First I will sellotape a piece of wire over a metre long to a metre ruler. Then will connect up a battery pack to an ammeter then the ammeter to the voltmeter then the voltmeter to the piece of wire using crocodile clips at 0cm then the negative clip is moved up and down the wire stopping at 10cm, 20cm and up to 70cm. Each time the length of the wire has changed I will read the ammeter and the voltmeter and record the results so from there I can work out the resistance which is R= V/I. Other variables will be kept constant like the voltage and the thickness of the wire. The experiment will be repeated three times using the same equipment.
Equipment List:
. Ammeter
2. Voltmeter
3. Power Pack
4. Power Leads
5. Two Crocodile Clips
6. Over 1 metre of wire
7. Sellotape
Fair Test:
I will make this test a fair test by keeping all the variables constant. By keeping the room temperature same each time and the same type of the wire the same each time. The wire will have to be pulled tight and tapped to both ends. Then I will carry out the experiment three times to get three sets of results. I can then work out the average and make graphs to show my results with a line of best fit.
Prediction:
I predict that if you increase the length of wire you increase the resistance. So if you decrease the length of a piece of wire you would decrease the resistance. This is because there are more atoms colliding with the electrons slowing down the electricity and causing a collision which produces energy called heat. The longer the wire the more colliding atoms there will be acting against the current producing a higher resistance.
Factors I have controlled:
Material:
The type of material will depend on the amount of free electrons, and the amount of atoms within the wire will affect the resistance.
Length of wire:
Depending on the length of the wire the resistance will either be high or low. So if the wire was increased the electrons would have a longer distance to travel therefore more collisions could occur on the way.
Wire width:
If the width of the wire is increased there is more space for the electrons to pass through. So due to the increased space between ...
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Material:
The type of material will depend on the amount of free electrons, and the amount of atoms within the wire will affect the resistance.
Length of wire:
Depending on the length of the wire the resistance will either be high or low. So if the wire was increased the electrons would have a longer distance to travel therefore more collisions could occur on the way.
Wire width:
If the width of the wire is increased there is more space for the electrons to pass through. So due to the increased space between the atoms there will be less collisions therefore less resistance.
The reason why I am investigating the resistance of the length of wire as it is the easiest to measure and would show a connection between the length of the wire and the resistance.
Results Table:
Voltage
Voltage
2
Voltage
3
Average
Voltage
Current
Current
2
Current
3
Average
Current
Resistance
AV/AC = R
0
0
20
30
40
50
60
70
0
2.03
2.48
2.64
2.79
2.79
2.90
2.96
0
2.11
2.49
2.65
2.79
2.80
2.90
2.98
0
2.09
2.49
2.65
2.79
2.80
2.90
2.96
0
2.076
2.486
2.646
2.79
2.796
2.90
2.966
0
0.96
0.64
0.46
0.36
0.29
0.25
0.22
0
0.98
0.63
0.46
0.36
0.30
0.25
0.22
0
0.98
0.63
0.46
0.36
0.29
0.25
0.22
0
0.973r
0.63r
0.46
0.36
0.293r
0.25
0.22
0
2.13ohms
3.93ohms
5.75ohms
7.75ohms
9.53ohms
1.6ohms
3.48ohms
Graphs
Analysis:
From my graph I can see that the resistance of the wire is proportional to the length of the wire. This is a very positive correlation. So my prediction was correct. The length of the wire increases so does the resistance. For example a wire 10cm long could have 500 atoms blocking the electrons. Therefore in a 20cm long wire there would be 1000 atoms meaning the resistance has doubled. I have noticed that the resistance has doubled every time the wire has been increased by 10cm. I also know this because the line of best fit goes through all of the results in a straight line showing I have carried out this experiment correct and it matches my prediction.
Conclusion:
My conclusion matches my prediction. That if the wire increases more atoms collides with the current trying to pass through the wire so there is a resistance against the current. So therefore if the length of the wire increases the resistance increases. Also if the length of the wire was trebled or quadrupled then the resistance would also treble or quadruple.
Evaluation:
From my results table and my graph I can see that my results I collected are very reliable. I know this because none of my results are odd and are not out of place on the graph. During the experiment I have noticed a number of improvements that could be made. The first improvement would be the circuit. Instead of connecting the voltmeter to the circuit I would connect it to the wire that is being tested. The reason I would do this is to only measure the voltage of the wire and not the other leads of the circuit. I would also put the ammeter at the other side of the wire to only measure the current of the wire and not the other leads. To expand on the investigation I would investigate the diameter of the wire.
Research
All materials, solid, liquid or gases are made up of atoms. The atoms themselves consist of a central bit, called the nucleus, made up of particles called protons (which have a +ve electrical charge) and neutrons (which have no charge) Orbiting around the nucleus are electrons which are very tiny and have a -ve electrical charge. One can think of the electrons orbiting in layers like the rings of an onion, and it's the ones in the very outside layer, the outer shell, that are the most important when thinking about conduction.
In metals, the outermost electrons are held only very weakly to the atom and often wander away from it and go to the nearby atom or one a bit further away. These wandering electrons are called conduction electronsand the more of these there are, for a given volume of metal, the better the metal will be as a conductor of electricity. When you connect a battery across a wire, one end becomes +ve and attracts the conduction electrons, which drift towards that end of the wire. But the electrons have obstacles to face because the metal atoms are jiggling about because of their thermal energy and so the electrons collide with them and are knocked all over. It's this difficulty that the electrons have in moving along the wire that we call resistance.
Resistance involves collisions of the current-carrying charged particles with fixed particles that make up the structure of the conductors. A resistor is a material that makes it hard for electrons to go through a circuit. Without resistance, the amount from even one volt would be infinite. Resistance occurs when electrons travelling along the wire collide with the atoms of the wire.
The unit of resistance is Ohms.
The higher the resistance, the lower the current. If there is high resistance, to get the same current a higher voltage will be needed to provide an extra push for the electricity.
Some metals have less resistance than others. Wires are always made out of copper because copper has a low resistance and therefore it is a good conductor. The length and width of a wire also has an effect. In this investigation I will investigate how the diameter of a wire will affect the resistance in the circuit.
Ohm's law
He discovered relationship that the amount of steady current through a large number of materials is directly proportional to the potential difference, or voltage, across the materials. Thus, if the voltage V (in units of volts) between two ends of a wire made from one of these materials is tripled, the current I (amperes) also triples; and the quotient V/I remains constant. The quotient V/I for a given piece of material is called its resistance, R, measured in units named ohms. The resistance of materials for which Ohm's law is valid does not change over enormous ranges of voltage and current. Ohm's law may be expressed mathematically as V/I = R. That the resistance, or the ratio of voltage to current, for all or part of an electric circuit at a fixed temperature is generally constant had been established by 1827 as a result of the investigations of the German physicist George Simon Ohm.
Alternate statements of Ohm's law are that the current I in a conductor equals the potential difference V across the conductor divided by the resistance of the conductor, or simply I = V/R, and that the potential difference across a conductor equals the product of the current in the conductor and its resistance, V = IR. In a circuit in which the potential difference, or voltage, is constant, the current may be decreased by adding more resistance or increased by removing some resistance. Ohm's law may also be expressed in terms of the electromotive force, or voltage, E, of the source of electric energy, such as a battery. For example, I = E/R.
With modifications, Ohm's law also applies to alternating-current circuits, in which the relation between the voltage and the current is more complicated than for direct currents. Precisely because the current is varying, besides resistance, other forms of opposition to the current arise, called reactance. The combination of resistance and reactance is called impedance, Z. When the impedance, equivalent to the ratio of voltage to current, in an alternating current circuit is constant, a common occurrence, and Ohm's law is applicable. For example, V/I = Z.
With further modifications Ohm's law has been extended to the constant ratio of the magneto motive force to the magnetic flux in a magnetic circuit.
Resistance values in electronic circuits vary from a few ohms, W, to values in kilohms, kW, (thousands of ohms) and megohms, MW, (millions of ohms). Electronic components designed to have particular resistance values are called resistors.