General Physics II Image: Conductor Sliding on a Pair of Conductor Rails

Because Canvas is so bad at copying images from one shell to another, here is another set of images used in one of my online tests or quizzes:

Version 1:

Version 2:

Version 3:

Version 4:

Version 5:

Version 6:

Version 7:

All of these show a conductor sliding along a set of rails in an uniform magnetic field.

Physics II Quiz Images: Coil of Current-Carrying Wire in a Magnetic Field

Because Canvas is so bad at consistently copying images from one shell to another, here is another set of images used for one of my tests or quizzes.

Version 1:

Version 2:

These depict a coil of wire with N turns which is carrying some current in a uniform magnetic (B) field.

Physics II Quiz Image: Velocity Selector and Charge Spectrometer

Because Canvas has trouble consistently copying images from one shell to another, here is a set of images pertaining to another of my online tests or quizzes:

Version 1:

Version 2:

These both show a velocity selector and a charge/mass spectrometer.

Virtual Lab: Voltmeter from Galvanometer

Since we are on lockdown at Troy University, I have been working on virtual or take-home labs to finish out the semester. I have produced two, which actually allow me to finish the semester. Here is the first of these two:

The basic premise of this lab is simple: I take all of the measurements, but I both overshoot and undershoot. Students must then decide the correct values for these measurements.

Physics II Quiz Images: Velocity Selector(s)

Because Canvas is bad at copying over images from one shell to another, here is yet another set of images which are going to be used for one of my quizzes or tests:

Version 1:

Version 2:

Version 3:

Version 4:

These basically show a velocity selector. There is present a uniform magnetic field in the -z direction, a uniform electric field in the +x direction, and a charged particle moving instantaneously in the +y direction.

Bonus: Here's a few with particle drift.

Version 5:

Version 6:

Lot's of possible questions from these, I think.

Physics II Labs Graph: Inverse Image Distance vs Inverse Object Distance

Because Canvas is so bad at copying images and graphs from one shell to another here is another graph used in one of the quizzes or tests:

This graph is for the image and object distances for a single lens.

Physics II Images: Two Resistors, a Battery, and a Switch

Because Canvas is so bad at copying images from one shell to another, here is another set of images used in one of my quizzes or tests:

Version 1:

Version 2:

Version 3:

All three consist of two resistors in parallel with each other, and a switch which connects or disconnects the second resistor from the circuit.

Physics II Images: 4 Bulbs Connected Together

Because Canvas is so bad at copying images from one shell to another with any consistency, here is another set of images used in one of my quizzes or tests:

This shows 4 lightbulbs connected to a battery as a circuit diagram. There are other versions of this diagram.

Version 2:

Physics II Images: AAA Battery

Because Canvas is bad at copying images from one shell to another, here is another image used by a quiz or test on Canvas:

This is a 1.5 V AAA battery.

Physics II Images: Bar Moving on Tracks in a Magnetic Field

Because Canvas is so bad at copying images from development shell to course shell, here is another image needed for one of my online quizzes or tests:

This shows a conducting moving with velocity v (moving to the right at speed v) along a pair of parallel tracks of separation distance d in an uniform magnetic field of magnitude B (pointing out the the page). The tracks are connected on one end by resistance R, which is large enough that the resistance of the bar and track will be negligible in comparison.

Light Bulb Experiment: DC Voltage?

In continuation of my previous post on this topic, I have set up my lightbulb with a 2.2 V DC voltage for 10 minutes and measured the resulting output voltage and current:

Over time, the current declines somewhat--exponentially, in fact--whereas the voltage measured across the bulb remains ~constant. The implication here is that the resistance of the bulb slowly increases with time, presumably until it reaches some quasi-steady-state temperature (and hence resistance).

The implication for this is that the "linear" regimes of the lightbulb's voltage-current curves aren't actually entirely linear. That said, they appear to be reasonably close to linear over the short-term (~2-10 seconds) considered in the ramps yesterday, at least as observed using a DC signal. In fact, I will close by posting a set of four more images, to compare the upper/lower linear regions for short time ramps to longer time ramps.
Here is the upper linear region linear fit with a 0.002 Hz frequency (500 s period):

And here is the lower linear region fit, for the same data:

Now let's look at a 0.2 Hz signal (5 s period), beginning again with the upper linear region:

And the lower linear region:

That's it for today. Next week, God willing, I would like to start looking at the intensity output for the light bulb. Preview question: if we treat the resistance as constant when the bulb is "on", we should expect to get what type of graph for intensity vs voltage and intensity vs current?

Light Bulb Experiment: Some Observations

I've connected a simple incandescent lightbulb to a PASCO 850 Interface setup which I'm using to provide power and also to measure current and voltage outputs, as well as a voltage sensor for the lightbulb itself. Additionally, I've connected a High Intensity Light Sensor to the PASCO 850 Interface to measure the light's intensity while I am doing this. The image below shows the basic signal generator information along with the Voltage sensor reading as a function of current output (data from the light sensor isn't shown).

I want to highlight a few points here, and maybe (no promises) add some follow-up posts.

First, note my general set-up: my voltage output is a positive ramp with an amplitude of 2.4 V, although there is some internal resistance in the wires and hence the voltage drop across the bulb itself is more like 2.3 V. I have a voltage limit of 2.5 volts--this is the limit specified by the light bulb which I am using, although with my ramp settings, I should not ever see this voltage output. The Ramp repeats itself every 2 seconds (0.5 Hz frequency).

There appears to be two approximately linear regimes for this bulb, with a pair of nonlinear transient regimes. There is also a "line" from "top" to "bottom", but this is an artifact of the ramp's repeating itself. The first "nonlinear" part of the graph is when the bulb is first turned on, and thus the filament rapidly heats up and its resistance increases. This region is the curving "tail" to the lower right of the higher linear region, and I will set this aside for now (it can be easily selected around by introducing a short delay to the data collection from when the signal is turned on).

The two "linear" regimes represent when the voltage is too low for the bulb to glow, < ~0.25 V, and again when the voltage is strong enough for the entire filament to be glowing, > ~0.9 V. The "S"-shaped transient region connecting the two is when the filament begins to glow, during which the slope (and hence resistance) actually increases somewhat, compared even to "hot" vs "cold" resistance (everything outside of the "tail" is basically "hot" resistance, albeit not steady state).

For what it is worth, the "resistance" (measured by taking the slope of the linear portion) is about 15.1 Ω for the upper "on" region and about 2.2 Ω for the lower region with these settings. Two other notes here: these values change somewhat if I change the ramp frequency, and also neither "linear" region is actually entirely linear. To the first note, I can offer this graph taken at 0.1 Hz:

The slopes are now 14.9 Ω and 1.76 Ω, respectively. These differences, especially the former, may seem small, but they are repeatable.

And for the second point, I will want to look at in a future post. Hint: it involves turning off the ramp and looking at just a DC signal.

Physics II Graphs: Capacitor

Because Canvas is so bad at copying graphs, here is another set of quiz graphs:

Graph 1:

Graph 2:

Graph 3:

All three of these graphs are for the same 0.25 F capacitor.

Physics II Graphs: An Ohmic Resistor

Because Canvas is so bad at copying graphs, here is another set of quiz graphs:

Graph 1:

Graph 2:

Graph 3:

All three of these graphs are for the same ideally Ohmic resistor. Pay attention to units!

Physics II Graphs: RC Circuit Charging and Discharging

Because Canvas is so bad at copying graphs, here is another set of quiz graphs:

Graph 1:

Graph 2:

Graph 3:

Graph 4:

Graph 5:

Graph 6:

Graph 7:

Graph 8:

Graph 9:

Graph 10:

Graph 11:

These assume a 0.5 mF capacitor charging or discharging through a 2 kΩ resistor with a 12 V battery (charging) or 12 V initial charge (discharging), and are taken for a time of 5RC.

Physics II Image: Kirchoff's Laws RC Circuit Quizzes Image

Because Canvas is so bad at copying images, here is another quiz image:

This circuit contains a battery with EMF ε and internal resistance r, which is connected to a capacitor of capacitance C and a resistor in series with the capacitor with series resistance R_S, and another resistor in parallel with the first resistor and capacitor with resistance R_P. There is a switch which can be open (shown) to allow the capacitor to discharge through the resistors R_S and R_P, or it can be closed to allow the capacitor to charge from the battery through the resistors r and R_S.

Bonus Images:
Switch open for discharging the capacitor

Switch closed for charging the capacitor

Some neat questions can come from these.