21st of April's Class
We started the day introduced to the understanding of how current flow in a circuit. In the image right below, the upper half was the first circuit that was shown to us.
Initially, the switch, located at the left side of the middle row, was opened, and both of the light bulbs to the right, marked with 1 and 3 was on. We were supposed to predict what would happen when the switch was closed. Our initial prediction was that all three would light up, but would all be dim. However, that was not correct, and the true result is that the bulb in the center would not light up at all, and the other two light bulbs would experience no changes at all. The current ignored the center portion of the circuit.
The next circuit Professor Mason presented to us was a little bit more complicated. The circuit is shown at the lower half of the previous image. The same question was asked, what would happen if the switch was to be closed. Initially, both the light bulbs were lit up. Our prediction was that the bulb marked with the number 1 would be brighter, due to the presence of an extra source of Voltage in its circuit.
However, upon experimentation, it was found that there was no change at all. Although during the demonstration, the brightness of both the bulbs were switched after the switch was turned on, Professor Mason explained that it was due to the difference in Voltage left within each battery, as the switch was closed, the flow of voltage was reversed, and therefore the battery supplying the energy for the respective bulbs were switched.
The image right below is the real-life set up of the first circuit mentioned earlier:
Voltage Law works similar to the Law of Conservation of Energy. Voltage is conserved throughout the circuit. However, Current behaves differently depending on the set-up of the circuit. In a series circuit, the value of current is the same at all points. While in parallel set up, its value would be distributed, and vary depending on the resistors present in the circuit.
Professor Mason then asked us to experiment with setting up our own circuit to achieve certain desired outcome. The next image depicts the experiment. The table was made rather confusingly, however, what it was asking is: Which set up would produce a bright light from the bulb, and which would produce a dim light from the bulb. We were to test it out by arranging the batteries in series/parallel and the bulbs too would be arranged alternatively in series/parallel.
We found that:
When the bulbs are arranged in series, they produce dim light.
When the bulbs are arranged in parallel, they produce bright light.
When the batteries are arranged in parallel, the bulbs produce dim light.
When the batteries are arranged in series, the bulbs produce bright light.
And we found a relationship between the brightness produced by the bulb with the Power that is present within the circuit; They have a proportional relationship. The larger the Power, the brighter the light produced by the bulb.
As it turns out, resistors can also be arranged in parallel and series. The calculation for the respective arrangement is also different. The following image depicts the simple formula for calculating the resultant resistance for parallel and series:
As the image above had shown, the calculation for the resistance of the resistors in parallel set up is slightly more complicated than its series counterpart, which is just the sum of all the resistor involved. Each of the ohm value of the resistors has to be powered by (-1) and added all up, the resulting value would then be powered again by (-1) to get the total value of resistance of resistors in parallel arrangement.
We were then taught about resistors and how to read their approximate resistance by reading the colors of the band on the resistor. We start reading from the side that has the smallest distance between a colored band and the end of the resistor (not counting the wire extension). The last band is the approximation of error, it gives a gauge on how accurate the resistor is from the value indicated on the resistor. The second last band signifies a multiplier, in multiples of ten, that was to be multiplied to the preceding digits to its left. The other colored bands signifies a digit, respective to its position.
We were then to use a multimeter to test out the resistance of each resistor, as shown in the picture above. We would then make a record of each reading and see if the value falls within the range of approximation of error. After experimenting, the following image shows the result we obtained from this.
We found that all of them fits within the range of value of error, with the exception of one. Located at the bottom left corner of the image, its degree of error is about 33%, which is way too much. However, we could not pinpoint the reason for the error, it might have been the fault of misreading the colored bands. At this point of time, the powerpoint slide that showed the values of each colored band was long gone. Therefore, we had no way to backtrack and see where we went wrong.
The final part of our day was spent learning about Kirchoff's Law. It is one of the fundamental laws that would help us gain an understanding as to how the elements within a circuit interact and behave. One of the most important understanding gained from this law has to do with the nodes of a circuit. The nodes of a circuit is basically a junction, where three or more elements in the circuit would meet. At this point, the input and output of the current has to equal zero. With this understanding, we can also predict the direction of the current and voltage.
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