ESD Association standards of static control. It is also acceptable to use the charge potential accumulated on a material for characterizing its electrostatic properties. In industry, to evaluate whether a work area is safe from potential static hazards, the working areas are classified into three different levels characterized by the discharge time and the charge potential Welker et al. Ratings for surface resistivity of antistatic finished textiles. Akinlabi, S. Electrical resistivity , an inverse of electrical conductivity, is a measure of how strongly a material opposes the flow of electric current.
Despite the advances in dissimilar joining, particularly joints between Al and Cu that is relevant to the electrical industry, limited information exists on electrical resistivity measurements of weld cross-sections produced [ 63 , 75 , 82 , 83 ].
Intermetallic compounds are usually formed as a result of increased temperature during the welding procedure. Against this background, the electrical resistivity of the welds conducted using various parameter combinations was measured and correlated to the heat input into the welds. The electrical resistivities were measured using a four-point probe meter, while the heat input was calculated using Eq.
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The torque values were steady state values obtained during the welding procedure. The results are presented in Table 6. Table 6. Electrical resistivities and corresponding heat input [ 14 ]. The electrical resistivities of the welds ranged between 0. The percentage increase or decrease in the resistivity of each weld compared to the average joint resistance are as indicated using the arrows.
The arrows pointing upwards indicate an increase, while those pointing downwards indicate a decrease in the electrical resistivities compared to the parent materials. It was observed that the welds with the highest percentage increase of 9. A graphical representation of the trend observed is presented in Figure 6. Figure 6.
Electrical resistivity vs. It was observed that for all the weld settings, the joint electrical resistivities increase as the heat input increases at constant spindle speeds.
An Investigation Into the Resistance of a Wire - GCSE Physics Coursework
This trend can be attributed to the presence of intermetallics in the hot welds. Very little variation compared to the average joint resistance of the parent materials was observed in the electrical resistivity readings from one weld to the other.
The weld settings employed in this research work can therefore be recommended to produce welds with low or no electrical resistivity. Many research investigations into FSW of dissimilar welds have confirmed that joints of various combinations have been successfully produced but characterized with the formation of intermetallics.
These results show that as the length of the wire increases, the resistance increases, as well. Furthermore, if you double the length of the wire, the resistance is roughly doubled. For example, when the length of the wire is 20cm the resistance is 3. In my main investigation I will see if this observation applies to my results. I found that the apparatus I used was suitable, but I think that I could possibly increase the number of data points to generate more reliable results, perhaps by increasing the length of the wire by 5cm each time, instead of by 10cm.
I predict that the longer the wire, the larger the resistance. This is because the free electrons in the wire bump into more atoms, thereby making it harder for electricity to flow.
Similarly, the shorter the wire, the smaller the resistance because there will be fewer atoms for the electrons to bump into, thereby easing the flow of electricity. Furthermore, the resistance of a wire is directly proportional to the length and inversely proportional to the area, so doubling the length of a wire should increase the resistance by a factor of two.
This is because if the length of the wire is doubled, the electrons bump into twice as many atoms, so there will be twice as much resistance. If this is correct, the graph should show a positive correlation. First, I will collect the apparatus I need and set it up as shown in Diagram 1, below. Next, I will set the power pack on the lowest voltage possible to ensure that the current passing through the circuit isn't too high which could potentially affect the results because the wire would get too hot.
I will place one crocodile clip at 0cm on the wire and the other at 5cm to complete the circuit. I will then turn the power pack on and record what voltmeter and ammeter readings. I will switch off the power pack, move the crocodile clip that was at 5cm up to 10cm, and switch on the power pack.
Again, I will record the voltmeter and ammeter readings and turn off the power pack. I will repeat this method every 5cm until I get up to cm, taking three readings from both the voltmeter and ammeter each time to ensure accuracy. To ensure accuracy I will record the voltage and the current three times every 5cm and take the average reading. This will reduce the chance of false readings and will cancel out any anomalous results. I will also ensure that the wire does not heat up too much by confirming that I do not set the voltage too high on the power pack and by maintaining the same the voltage for every reading.
In addition, I will make sure I turn the power pack off after each reading. I will try to make this investigation as accurate as possible. There are different variables that can be changed in this experiment; these are the independent variable. However, due to my line of enquiry, I will only change the length of the wire. The variables I will control will be the type of wire resistivity and the cross-sectional area of the wire. I will also control, using the power pack, how many volts pass through the wire.
Below is a table illustrating the effect of changing the variables see Table 2 :. I will ensure experimental safety by confirming that all the wires are connected properly and that none of the insulation on the wires is worn. I will also ensure that there is a clear indication that the power is isolated by means of a switch and an L. I will stand up during the investigation to ensure that I do not injure myself if something breaks. Below is a table of my results Table 3. I have taken three reading and have worked out the average, shown in red.
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Table 3 shows that as the length of the wire increases, the resistance increases, as well. This confirms the first part of my prediction: that the longer the wire the larger the resistance.
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In addition, my prediction that doubling the length of the wire increases the resistance by a factor of two is correct see Table 4. Graphing these results shows a nearly straight line, illustrating a strong positive correlation between length and resistance, which is consistent with my prediction. Overall, my results are very consistent with my predictions. Most of the data points were on, or very close to, the line of best fit.
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There are a few data points that are farther away from the line of best fit than the others, but they are still consistent with the general trend. There are no anomalous results that I would consider to be far away from the line of best fit. There are possible sources of error that might have led to inconsistent results, such as a kink in the wire. This would have prevented the area of the wire from remaining constant and would have affected my results. However, I made sure that the wire remained straight throughout the experiment.