Wed. Week 8, April 16: Resistors and Circuit analysis

On this day, the class went into further detail of electric circuits by focusing on the subject of circuit analysis. Particularly, we spent a large portion of time discussing the various ways in which a number of resistors could be connected together and how the various combination of ways to connect resistors can affect the overall resistance of the total circuit.

At the start of class, we were tasked with repeating the steps we took in the previous quiz where we had to connect two bulbs in a way to get either both bulbs dim or both bright.
After this was accomplished, we treated the bulbs as resistors and started taking voltage readings at points on both circuit configurations. We then solved for current at these points in both circuits. The values were then compared and a pattern was discovered regarding the configuration in which the bulbs were hooked up the the circuit.

This observation led to a discussion on equivalent resistance of resistors in parallel and series. The overall resistance of resistors in series is simply the summed up resistances of each resistor and the overall resistance of resistors in parallel are summed inversely.
With this knowledge, circuits made up of parallel and series combinations could now be reduced to a simpler circuit made up of equivalent resistances.


To demonstrate this property of resistors, the class first calculated the equivalent resistance of a given parallel-series circuit and then compared that value to the measured resistance of the built circuit. The two resistances proved to be equal to each other within the range of the resistors' tolerances.

Mon. Week 8, April 14: Electric Potential

Today's topic of discussion was primarily focused on the subject of electric potential. Different from electric potential energy, electric potential is another word for describing voltage and is defined as potential energy per unit charge.

At the start of the class, we were given an exercise where we calculated the potential between each of twenty evenly distributed segments of an symmetrical geometric object at some point from the object.

The next major experiment dealt with taking live measurements of potential at different points between two points across a conductive sheet of paper. Fifteen volts was applied to the two strips of metallic paint shown on the paper. We measured voltage at points between the paint with respect to the round blotch of paint (not the long strip).

The data gathered from the potential measurements suggests that the potential increases non-linearly

Wed. Week 7, April 9: More with circuits

For this day, we went more into depth on the topic of electric circuits and their properties.

At the beginning of class, we started with a quiz that tasked us in developing a way of wiring a series of two light bulbs in a configuration where one light would be dim, or both would be bright. The secret to success on this quiz is being familiar with the properties of series and parallel circuits. The bulbs wired up in a parallel to the voltage source would both be bright since the voltage down each branch would be the same as the voltage at the source. The bulbs wired in series with the voltage source would produce a bright and a dim bulb since there is a voltage drop across the first bulb, causing the second bulb to be powered with lesser voltage.

We then viewed a demonstration on the relationship of power and heat. The cup was filled with a saline solution that was used as a conductor between two electrodes. Voltage was applied to the electrodes and a temperature probe measured any increase in temperature of the solution.

From the graph generated by the temperature data, we could solve for values such as resistance and current. The sharp jump in the graph corresponds to an increase of the voltage settings.

Toward the end of class, we watched another demonstration regarding the generating of heat using the internal resistance of food products as a circuit's load. With a high enough voltage, the power through the hot dog was enough to char the ends where the electrodes were attached and cause some mild smoking. Another experiment was performed from the hot dog set up, which dealt with the how the spacing of LED leads would contribute to the power generated by them. It turns out that the LED that was stuck into the hot dog resistor with the largest lead gap was the one that generated the most power. This observation was due to the fact that the wider lead spacing directly related to a larger potential difference across those leads.

Mon. Week 7, April 7: Ohm's Law

On this day in class, we temporarily abandoned the topic of charge and its behaviors in order to start going over the subject of circuit fundamentals. In particular, were went over the ways in which an electrical circuit's voltage, current and resistance were all related to each other.


For the first experiment of the day, our groups collected data from an voltmeter and ammeter attached to a circuit with a fixed resistance and voltage. Data was taken from numerous voltage settings. The circuit was made up of a power supply and a single resistor of wound up wire.

The collected values were inputted into a spreadsheet where they were then used to generate a graph that turned out to be linear in nature. We then came to the conclusion that the slope of the volts vs amps graph is the value of the resister's resistance. After realizing this, we then compared our values to another groups, compared our resisters, and drew conclusions based on the physical qualities of the resistor and its corresponding resistance. We discovered that the length of the wire used to make the resistor was proportional to the resistance.

We expanded on this concept in the next lab experiment, which consisted of measuring the  resistance of a multitude of coils with different lengths. After generating a graph for resistance vs. length, the data showed a linear and proportional relationship between resistance and wire length, confirming our observations from the previous lab.