Day 1 - Tuesday - 24 February 2015 - Solderless Breadboards, Open-circuits and Short-circuits

Today was the start of Spring 2015 Engineering 44 with Mason!
We started by analyzing a circuit with 5 electrical elements: two identical batteries and three identical light bulbs. They were arranged as shown in the picture below.

The question was: what is going to happen when the switch is closed? And, my group answered the following:

We said that the top bulb would remain the same which means option C, the bottom bulb would get dimmer which means option B, and that the bulb in the middle would turn on which is option A. However, our answer was incorrect because, when switch is closed, there is no drop in potential across the middle light bulb. In other words there is no current flowing in that segment of the circuit.

Prof. Mason then set it up for us to see what happens.

The top bulb and bottom bulb remained the same and the middle bulb did not turn on.

Then we discussed charges and currents as the time derivatives of charges and this lead to the next problem.

After making a mathematical description of the charges, we drew what the function for current would look like.

The drawing for the charge as a function of time is at the left and the current as a function of time is on the right.

Then we solved another problem where we worked the concept the other way around.

And our answer was:

However the actual answer was 0.4908 mC because we were calculating the charges from t = 0 to t = 2. If we were calculating the total charges for 0 < t < infinity, then the answer would be 0.5 mC.

Then we had a discussion about voltage, power and energy where we described their relationship mathematically, and then we did a concept check problem.

So we wrote the problem on the left side of the board and our answer on the right side of the board which was verified to be correct because of the equation written on the bottom on the board.

Then we did our lab.

Solderless Breadboards, Open-circuits and Short-circuits

Our first laboratory consisted of probing and learning the connections in a breadboard. We used a multimeter to measure the resistance between different points of the breadboard and see which spots offer a better connectivity and which should not be used.

First my group members and I checked the resistance of two holes in the same row. We measured a resistance of 0.6 ohms. Since there was current running from the multimeter across the breadboard and back to the multimeter, it can be considered a closed circuit.
Second, we checked the resistance of two holes that are on the same row but across the central channel. The multimeter could not measure the resistance between those two holes because it was too high. Since energy was simply dispersed and did not lead anywhere, it can be considered an open circuit.
Third we looked into the resistance of two holes that are not on the same row and across the central channel. The result was the same and we couldn't obtain a number for the resistance as it was too high. This can also be considered an open circuit.
In the last part of the experiment, we connected two different rows with a jumper cable and measure the resistance between the holes of those two rows. It turns out that the jumper cable opened a passageway with very little resistance for the holes in those two rows. The resistance that we measured was 0.9 Ohms. The running of current indicated that this is a closed circuit.