2/26/2015

We began the day with a circuit puzzle. We were asked to explain what would happen to the light bulbs when the switch was closed.

Switch open

Switch closed

Lab set-up

The first lab consisted of supplying a certain amount of voltage through a 100 ohm resistor. We supplied different amounts of voltage using a program called WaveForms.

Measuring the resistance of the resistor

We first measured the resistance of the resistor which was found to be 97.4 ohms.

Results

We then supplied different voltages across the resistor using WaveForms and then measured the current for each voltage.

Circuit diagram for lab

Graph of Current Vs. Voltage

It was found that the relationship between current and voltage was linear. (V=IR)

Lab set-up

The second lab required the use of a MOSFET and a 100 ohm resistor. The purpose of this lab was to determine the threshold voltage. We did this by increasing the voltage across the MOSFET incrementally and measuring the current. When the current begins to be roughly the same as the voltage is increases, we have determined the threshold. 

Results

We determined that the MOSFET voltage threshold was roughly 2.5 volts.

Summary:
The day consisted of learning or relearning ohm's law and Kirchhoff's loop law. Kirchhoff's loop law states that in a closed circuit the sum of voltages is equal to zero. Ohm's law states that the current through a circuit between two points is directly proportional to the potential difference across the two points.

2/24/2015

Circuit made

 The class began with a demonstration of a circuit involving two batteries and three light bulbs. We were to predict what would happen if the switch in the middle of the circuit was to be closed. Two bulbs on the outer part of the circuit are lit.

Prediction and drawing of circuit

We predicted that when the switch was closed, nothing would happen to the bulbs,

Circuit with switch closed

Our prediction turned out to be correct, because the potential difference is what causes the light bulbs to light and because the batteries are the same there is no potential difference created.

Charge vs. time and Current vs. time graph

 We were given a charge vs time graph and were asked to graph a current vs time graph based on the information given. We first set up a function for the charge graph and using that equation we were able to differentiate it and find the function for a current vs time graph relating to it.

lab set-up

The lab today consisted of using a multimeter and breadboard to measure resistance and determine if the location at which the probes were placed would be considered and open or closed circuit.

Results

Above is our results for the lab.

Summary: Today consisted mostly of making graphs and determining functions for those graphs when given a specific piece of information. We learned that current is the change of charge in time or the flow of electrons. We also learned that voltage is the work done by unit charge and power is the work done due to time. We also know that the sum of power in a circuit is equal to zero.