Day 24 - AC Circuits

Day 23 - Inductors

Day 22 - Solenoids and Magnetic Fields

Day 21- Magnetic Field of the earth

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The makeshift contraption above was used in order to determine the magnetic field of the earth.

Our group used what we knew about the Biot-Savart Law in order to calculate the magnetic field of the coil using the current, radius, number of turns, and the constant given. The relationship between the magnetic field from the earth and coil were used to determine this field. We based our calculation of the field based on the direction the compass was pointing, measured approximately in degrees. W had a known current and solved for the earth's field by dividing the coil's field by the tangent theta. The graph of the coil's field vs tangent theta is given below:

We used a general line of best fit and the slope was 1.055*10^-5 T

 

Day 20 - Motors & Magnetic Field Lines

Magnetic Motor Lab

Attaching the power supply to the motor caused it to spin.

Reversing the current's direction causes it to spin in the opposite direction.

Our Motor

The motor that our group created was composed of copper wire, several magnets and paperclips, and a power supply. A symmetrical oval shape was formed from the wire. One lead was sanded down 360 degrees while the other lead was sanded down half that amount. The paper clips were used as mounting points for the copper wire and placed on the top of the cup, and a magnet was placed inbetween the contraption as shown above. The current from the power supply is what moves the current through the wire and causes it to turn.

Day 19 - Magnetic Field

Magnetic field about a bar

We used a compass in order to find the magnetic north of the magnet. We indicated where the north and south poles were, and drew arrows around the magnet to represent the direction of the magnetic field. 

  

Visual representation of Magnetic field with ancient technology.

Magnetic Field and Rod

Attempt at solving for the magnetic field B for the metal rod. The units did not work out very well.

Magnetic Field with rotation

Calculation of Magnetic Field

Day 18 - Diodes and Transistors

We were able to create an amplifier on the breadboard shown below, according to the diagram shown above:

This breadboard set up created an amplifier that increased a 3,000Hz wave at 0.3 V with a transistor of 2N3904

This resulted in a 100 times amplification from the original.  The two waves on the screen are the wave being emitted by the function generator, as well as the amplification from the breadboard. The original voltage was 0.3 and the new one was 20-30 V.

We created the amplifier below based on the diagram shown above, using an LM386 audio amplifier

This set up finally did produce sound that we streamed from an alternative rock soundtrack from Bianca's phone, but it was mainly static.

Day 17 - Electronics and mystery box

Measuring Delta V

For this experiment we attached a function generator to the oscilloscope and set it to a frequency of 96Hz. We got the sine wave above as our result. We needed to find the theoretical and experimental period. To find the theoretical period we used the formula t=1/f. T is the period. We knew the frequency since we set it, so we plugged it in and got a period of .010417 s. We found a value of 5.1 for the wave's period and divided it by the time of 2 milliseconds. This gave us our experimental period of .0102 s, which is very close to the theoretical period. 

The two photos below are what occurs when the sine wave is changed to a triangle wave or square wave, respectively.

DC power supply

Our goal was to find the amplitude and period for this part. We found the amplitude to be 39 mV, while we were unable to find the period.

                                                                                                   AC Transformer

For alternating current, we needed to find the amplitude and period again. This was feasible since it was in the form of a sine wave. The amplitude was 20V and the period was .01702 (8.51*.002). The frequency was found to be 58.8 Hz

                                                 lissajous figures

The same alternating current transformer was connected to ch 1 and the function generator was connected to ch 2. The generator's frequency was set to 30 Hz and the oscilloscope was set in such a fashion that we could see the lissajous figured in the XY mode, for the two channels. The figure shown above was at 30 Hz, and it rotated and twisted as time passed.

In the photo above, the shape was an oval after we set the function generator to 60 Hz, and it should be noted that this one also rotated.

Mystery Box:

We had to decipher a Mystery box by determining which waves and frequencies it had. Our findings are below:

Red and Black

Square Frequency

Amplitude=4 V

Period=0.0044 s

Red and Blue

Square Frequency

Amplitude=1.8 V

Period=0.0043 s

Red and Green

Square Frequency

Amplitude=4 V

Period=0.0042 s

Blue and Black

Square/Sinusoidal Frequency

Amplitude=0.02 V

Period=0.003 s

Green and Black

Sinusoidal/Square Frequency

Amplitude=0.008 V

Period=0.0044 s

Other color combinations were possible, but nothing good came out of them worth mentioning. The yellow outlet did not produce any visible waves in combination with the others. The same goes for other combinations that were not mentioned. We were able to infer from this that the mystery box had both sinusoidal and square frequencies in it.

Day 16 - RC circuits

Quantitative Measurements on an RC System

Our experiment required that we make an RC circuit with a power supply, resistor, and capacitor in series. The resistor is used to slow down the charge time in order to make it more clear. The capacitor was shown on logger pro via a voltage measuring lead. Our group was able to initially predict that there would be an inversely proportional relationship between Potential and Time. This is shown on our graph below.

Based on the graph of the Discharge represented by the lower pink curve, we were able to conclude that the value of the constant B in the exponential equation should be close to zero. Also, the value for A in the equation should be close to the original voltage of 4.5 volts from the power supply.  Finally, the charge time should be the same for both the charge and discharge.

We found our experimental Charge time to be C=.00362 seconds. The theoretical charge time was found by using an actual measured resistance value of 21,500 ohm's, and plugging it into the equation tau=1/RC. With the capacitance known we found the theoretical time to be .00465 seconds. This was a 22 percent error deviation from our measured value. This is most likely due to the fact that some of our capacitor values were based on what they were labeled which were incorrect.

Day 15 - Capacitors

Our group performed an experiment in which we were to verify the relationship between distance and capacitance. We used an old physics textbook with varying degrees of separation based on the number of pages, as well as two sheets of aluminum. We used distances of 1, 10 and 20 pages of separation within the textbook. We obtained our capacitance values and graphed them, and found their to be an inversely proportional relationship between the distance and capacitance. As the distance increased, the capacitance decreased significantly. Our kappa value that was based on the first trial was .367, slightly off by a factor of 10 from the theoretical value of 3.5 for paper.











Later for the class experiment we were presented with two capacitors in which to measure the capacitance of. We found them to have 1.088 and 1.165 micro farads, respectively. We then proceeded to set them up in series and in parallel in order to measure the resulting capacitance values. By doing this we were able to verify the theoretical knowledge that we have been taught in class; that when capacitors are in parallel their capacitance values are simply added, and when they are in series their equivalent capacitance value is found in the same way that equivalent resistance of a parallel resistor is found, with the equation shown below.

Day 14 - Circuits in Series and Resistors

Lab Manual:

-Voltage measurements

Based on our measured values there was no voltage loss at all, since the initial and final values were the same. The current is also constant in the circuit.

-Parallel circuits

Based on what we measured both voltages remained constant in the parallel series resistors, and the initial and final currents are the same.

-Measuring resistors

We learned how to decode resistors by knowing which color bands stood for what value, and we could see if their color coding reflected their actual theoretical value by measuring them.


Equivalent resistance challenge problem:

Our group was given the series of resistors above and was asked to find the equivalent resistance. I was able to calculate it by doing each section individually and then breaking it down into several steps. We found the resistance to be 52.17 Ohm's. We then set up a real life version of this circuit, shown below:

The actual measured resistance of this system was 51.9 Ohm's which is very accurate considering we were using cheap 1/10th of a cent resistors.

Application of the loop rule several times

We were presented with the complex circuit above and found 3 equations in order to solve for the three I values. Eventually we were able to substitute the equations back into eachother to find alll the values, as shown below. Our values were actually incorrect because an arithmetic error was made at some point, since a calculator gave us values of 1.14, 0.99, and .14 amps, respectively.

In order to verify what we just got on the calculator, we set up a breadboard pictured below and measured the values which were 1.15, 1.005, and 0.148, respectively. In contrast these are very close to what we calculated theoretically.