Lab 18: CRT, Oscilloscope and Mystery Box

 Professor Mason set up a CRT (Cathode Ray Tube) , which is a vacuum tube that contains electron guns and focusing plates at the inside. By adjusting the voltage, it is possible to stir the light beam in the direction of the focusing plates; however, depending on the charge of each plate the graph varies.

 Using an oscilloscope, Professor Mason explained that if we change the period or frequency too much, it produces a dot going horizontally until the point it becomes a straight line because its going too fast. As shown in the below picture.

 Here, we added a battery, the result was that the voltage increased, so the graph moved vertically up.

 We derived acceleration by using the second law of Newton (F = ma) and Lorentz force (F = qE). Also we derived the vertical component of velocity. Vy = at. We know that time is just distance over velocity. So, we plug in acceleration and time into the Vy function.

 We used a function generator along with a speaker to test the sounds it produces when changing the frequency and voltage. First test case was sine wave set at 96 Hz. It produced a low deep hum sound. Second case was triangle and square wave, the triangle sound even deeper than the sine wave; however, the square one has a high pitch bee sound. When increasing the frequency, the pitch increases as well. When increasing the amplitude, it makes the sound louder.

Sine wave output.

 Square wave output.

 Triangle wave output.

Here, we can see the noise showing on top of the DC power supply that output 5V with triangle waves. This noise is periodic with period of 60Hz. AC coupling lets you take a DC signal in order to see if there is noise by zooming in.

 Professor Mason graphed a circle using two function generators at the same frequency.

Mystery Box

Using the mystery box, we plug in Black and Red, and we found out that the red one is an alternating current by looking at the graph.

 Black and Yellow has no changes, meaning that yellow is direct current because it shows a straight line without holes.

 Black and Blue gives 5V, also Blue is direct current.

Black and Green gives 8.5V, Green is direct current.

We plotted this graph to show the voltage of each color. There was a mistake with the names, blue and green supposed to be switched.