Electronic Systems - Investigate sensing devices in relation to environmental changes.

Vincent Ocasla

Physics Course Work – Electronic Systems

Aim:

Investigate sensing devices in relation to environmental changes.

Prediction and Hypothesis:

I predict that we can be able to detect changes in the environment by using sensing devices, which include LDR’s for detecting light intensity, thermistors for temperature, and other input sensing devices that vary in resistance in relation to the environmental changes surrounding it. We can use a morting device to detect the change in resistance by simply altering the environment. Sensing devices are simply input devices that detect changes in the environment.

A sensor such as a thermistor works by the heat energy hitting the very atoms of the actual wire that makes the sensor, it hits the electrons, which then allows the electrons to flow through the wire. This increases the current and reduces the resistance and that is why thermistors allow resistance to decrease when temperature increases. Again, the same happens with light emitting diodes, in which the photons of the light allow itself to hit the atom’s electrons until the electrons flow to produce a current, and the photons bounce away. This reduces the resistance to allow greater current. This increase of current reading in these sensors can be converted into a direct digital display of whatever it is the sensor is measuring.

This happens because as the level of energy increases, it allows these so called “electrons” to spin faster and faster, and those that are moving, due to the flow of energy caused by the direction of current due to some strange law of physics, it allows this flow of electrons to increase. Moreover, beta rays contain just fixed electrons flying about that hit these atoms to add to the rest of electrons, which to, contributes to the amount of electron flow. Heating may occur which can cause a disruption in the constant internal temperature (not to mention that nothing really is at a constant – it is constantly varying) and therefore increases resistance and decreases the current flow, resulting in a bouncing off of beta rays from the sensor/wire, giving a false reading.

The following members I am going to state that I am going to change include: the alteration and the modification of the one of the variables throughout this so called “experiment” and keeping the “rest” “constant”. The variables we are going to modify are the light intensity that is being directed at the LDR. The variables we are going to keep constant is the external temperature of the conductor, the current flowing through it (not in general, but from the power source (which is not relevant)), and the distances that are in relation to the irrelevance of the wire that is attached to the sensor unit. We expect many weird and wonderful things to happen such as the maximum resistance at absolute darkness, and no the minimum resistance at absolute lightness.

I will be investigating upon the relationship between resistance and the light intensity to determine whether my hypothesis is correct. On other notes, light intensity is measured in candelas.

Plan:

Apparatus:

1 LDR
1 Morting Device
1 Direct digital display unit with its LDR

Method:

This is a preview of the whole essay

I will be investigating upon the relationship between resistance and the light intensity to determine whether my hypothesis is correct. On other notes, light intensity is measured in candelas.

Plan:

Apparatus:

1 LDR
1 Morting Device
1 Direct digital display unit with its LDR

Method:

Set up the apparatus as shown above and then focus both LDR’s in the same direction, at a light source. Set the morting device to resistance. Read off from direct digital display unit and record light intensity. Read off resistance and record all information in results table. Repeat this 10 times, each with a different value of light intensity, making sure they are not to similar in comparison.

How we made it a fair test:

We made it a fair test by only changing one variable for each experiment. This was the light intensity

How we will change our input variable:

We will change our input variable by moving one of the crocodile clips along the nicrome wire, until the desired position of length is set. Our input variables are 60, 50, 40, 30, 20, 10, and 5cm. We are testing 5cm to see what effect this would have on our results, in relation to the heating effect.

Preliminary Experiment:

We carried out a preliminary experiment to see what happened if we kept our voltage at a constant of 1 volt to see what would happen to the current on each pair of wire thickness.

Preliminary results:

Voltage = 1 V

Diameter = 0.00028m

From the preliminary work, it shows that having the current to being adjustable, it was impractical due to the heating effect. Therefore it is decided that the current should be kept at a constant and that voltage should be adjustable.

Final results:

Current = 1 A

Diameter = 0.00056m

Diameter = 0.00028m

Diameter = 0.000375m

The results above were the final results after the improvements made on the preliminary experiment. The results show that the thinner wires needed more current than the thicker wires, apart from the length of wire where the longest wire had to have more voltage than the shorter wires. The resistivity of the three types of nichrome varied.

Conclusion:

I concluded that the increase in the length of a conductor would result in the increase in voltage, and the increase in the cross sectional area will decrease the voltage, and vice versa. This is because current flowing through a longer wire would require an increase in voltage in order to keep the flow of electrons the same, compared to a shorter wire because there is more resistance for the electrons to resist due to more particles in length. Therefore, more voltage is needed to overcome this resistance in order for the current to remain constant. For example, if the length of a wire doubles, the resistance also doubles. This would mean doubling the voltage in order to keep the current at a constant as shown in the results (provided the cross sectional area and the external temperature to remain constant).

Thus, current flowing through a larger cross sectional area, would require less voltage in order to keep the flow of electrons the same, compared to a smaller cross sectional area which requires more voltage because there is less resistance for the electrons to resist in a larger cross sectional area due to more space for these electrons to flow in. For example, if the cross-sectional area of the wire doubles, the resistance halves and therefore the voltage halves (provided the internal and external temperature, and length of the wire is kept constant).

As from the prediction and hypothesis of this investigation, the reason why voltage increases with current, is explained using Ohm’s Law, where V α I

The reason why voltage increases with resistance, is also explained using Ohm’s Law, where V α R and so combining them, we have V = IR

Because these values are influenced with sizes of the length of the wire, cross sectional area of the wire, and resistivity, in which from the experiments, voltage is proportional to the length of the wire, and inversely proportional to the cross sectional area of the wire. Resistance is also proportional to voltage and current was inversely proportional to voltage in this case, and so the following relations can be made.

V/I = R = ρl/A So as the voltage doubles, the length doubles, and if the area doubles, the current doubles, where resistivity stays constant.

My results show that resistivity was at a different constant for the different diameter wires. I was able to calculate the resistivity by rearranging the order of the formula.

ρ = RA/l

In addition, the straight lines on the graph proves direct proportionality which goes back to prediction.

All of the predictions have been proved, and evidence has been fully obtained through mathematical equations and results, and have been thoroughly analysed.

Evaluation:

The experiment proved to be a success and it went very well as the results were all well matched together from the preliminary work to the final experiment. The quality of the results was fairly accurate, although the curvature of the line graph on the test about the relationship between the length of the wire and voltage could have been improved.

Overall, the experiment went very successful, because a large majority of the results were very accurate, and are very closely linked. The experiment was very straightforward, and very easy to follow. Although the whole experiment went according to plan, the method could have been improved by including the improvements after the preliminary work, and maybe to also include a more variety of lengths and diameters of the nichrome wire, and to test them more than three times. In addition, we could improve the apparatus in which, we could have used a straighter nichrome wire, and have the measurements more reliable, in order to make the test more accurate.

From this, the reliability of our results could have been enhanced by considering these factors. Currently, the reliability of our results are fairly, reasonable, since the constants did not change too much, nor our input variables which were the lengths, and so managed to keep it to a good standard of accuracy. In saying this, the quality of it all is therefore good enough to support and prove my conclusion. Despite of this, those anomalous values must have been caused by the fluctuation of the reading value, due to disturbances whilst collecting the data, such as, movement in the wires position, and the change in temperature.

Not only should we carryout an improved experiment as explained above, but to also extend the investigation on what other factors affect the size of the electric flow, in relation to the actual aim. This may include the mass of the wire we are testing, and the density, or even changing the temperature to make it more interesting. We could do results that show the relationship between much of the other variables, such as, the resistivity of the wire in relation to the voltage etc. We could extend in adding m more formulas in order to check and prove our predictions.

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