Flexible Lab Request Sheet

Are you a Science Teacher? Do you have trouble keeping your lab equipment requests organised?

At the school I'm working in now, there are so many science teachers that laboratory equipment really needs to be handled by dedicated staff to prevent clashes, fix breakages, and manage inventory. For me this presented a new challenge because I was accustomed to digging through the supply closet myself and pulling out whatever I wanted on the day. Now I have to have my lessons planned more than a week in advance. I have to actually be organised!

The big issue there is that in the space of a week, a lot tends to change. I found that I was spending too much time chopping, changing, and re-thinking plans I had already laid out. Flexibility in planning will always be necessary so instead I did the next best thing and made my planning process more adaptive. I wrote a Google Sheet that automatically organizes and re-organizes my lesson plans. Major features of the Planning Template include:

• Planning is done chronologically in a single column for easy cutting and pasting big blocks of lessons.
• The planner automatically fills in a week-by-week template of what equipment needs to be delivered when based on the chronological plan and automatically updates based on any changes
• Disruptions (like holidays, or sick days, or surprise assemblies) can be added on the fly and the week template will adjust.
• The planner can be shared with students, parents, and colleagues so that everyone can know what is going on, and when.

Walk-through of features and set-up

If you want to try out the planner for yourself, you can go for it! You'll need to make a copy of the file to use it yourself:

Make a copy

Winning the "Pick Things Up for Me, Daddy" Game

I guess my daughter is still too young to intentionally drop things on the floor so she can watch me pick them up, but I think I'll try an ounce of prevention.

I picked up a suction-cup hook from Daiso meant for hanging your loofah in the shower. I replaced the hook with a length of ribbon and a small carabiner. The suction cup sticks to the surface of her high-chair and the carabiner can clip to most of her toys.

I think I might cut the ribbon to be a bit shorter so that:

• Toys don't fall off the edge of the chair at all
• the ribbon presents less of a strangulation hazard.

Pictured: Strangulation Hazard.

Or maybe I'll try a slip-knot so I can adjust the length as needed.

Bored Taking Notes? Turn Word into a Colorful Disco Dance Party

I don't know why I made this. I have a feeling I will regret unleashing this creation on the world. A created a Word document in which all the letter, number, punctuation, space and enter keys are all bound to a macro that changes the background color, font color, and font size as you type. The result looks like this:

A Terrible Thing

You can download the word document with the embedded macros here (requires Word for Windows. If you have Word on Mac you can use this version. Changing background colors is not supported in Word for Mac).

I typed up instructions into the document for you. It looks like this:

1) You must download this file and enable macros for this document to work

2) If nothing happens when you start typing, press Alt+F8 and run the "Add Binding" macro

3)  To end the typing party, press alt+F8 and run the "RemoveAllBindings" macro

4) To view or modify the functionality of this macro press alt+F11

ChargeLab 1.01 - Famous Last Words

"I think I'm finally done with ChargeLab."

I should have known better than to boast. In version 1.00 I re-thought how I calculate potential so that at large distances potential approached zero, and at near distances it approached + infinity. What I didn't notice is that this adjustment completely broke the way that field lines lie. I'm releasing version 1.01 with the following features and fixes

1. Re-worked the way that field lines propagate so that they come out smoother and intersect less frequently.
   
2. Reverted the method for calculating potential so that the field strength inside of charged surfaces remains zero.
   
3. Remove the ability of the user to measure potential. This is really just a hack to hide the fact that the values of the potential don't work out as expected.

Reverted Potential Calculation correctly identifies the field strength in the center of a charged surface as zero. 

New Smoother Field Lines!

I think this will be the last version. Not because there is nothing left to do but because I am well and truly stuck. The problem is that the formulas we are used  to seeing for calculating potential and field strength in our three dimensional world don't seem to work in a two dimensional simulation. To adjust for the missing degree of freedom in which charges can move, I modified the formulas:

F = Force
V = Potential
k = Coulomb's constant
k' = An arbitrary constant
q = charge
r = Distance from charge's center

To transform the formulas into two dimensions I integrated with respect to distance, r. This seemed to do the trick for Force and Field Strength:

There are no negative distances in this simulation and both functions behave very similarly in the first quadrant. With these changes I got the slight change in behavior I needed. Charges spread out on the edges of surfaces and produced no field strength within surfaces.

The problem comes in when we look at the structure of Potential in 2 and 3 dimensions:

In 2 Dimensions, the natural log has much different behavior to the inverse function found in three dimensions. In 2 Dimensions there is a finite, non-zero distance from a charge where the potential is zero. Beyond this point, the potential changes sign and grows slowly to infinity. I'm struggling to understand the significance of these differences but I observe that they produce the desired potential gradients in two dimensions. 

I would be interested in hearing your thoughts on this puzzle.

• Are the transformations above appropriate or do they only appear to work by coincidence?
• Is there a better way to simulate forces and potentials in two dimensions?

You can download the latest version of ChargeLab here.

Source code available here.

ChargeLab 1.00 - Simulating Electric Fields

I think I'm finally done with ChargeLab. I made a few fixes and I'm pretty happy with the final result. The new features are:

1. The number of field lines coming out of charges are now proportional (roughly) to their charge
2. Fixed the bug where potential was zero at the center of charges. Now it's zero at infinity.
3. Fixed a bug with termination of field lines. This should speed up field line calculation as well as help prevent field lines from terminating in empty space.

The Field Line Density is higher where the Field Strength is higher.

You can download the latest version here.

Source code available here.

New Videos: Falling through Tunnels in the Earth

This is a classic question that I remember seeing when I was a high school student: "How long would it take to fall through a tunnel through the Earth?" My Physics teacher solved the question for us and I'll have to confess only understanding the solution for about 30 minutes. Today I went back and re-worked the question myself. I've presented the solution in two parts.

First, what is it like to fall straight through the earth:

Second, what if the tunnel doesn't go through the Earth's center? What if you want to connect NY to LA for example?

IB Physics Graphing Template for the 2016 Syllabus

Update: The New IB Physics Graphing Template for the 2016+ Syllabus is out! Follow this link to find out more!

This is a work in progress so stay tuned for updates, but I've been re-working the physics graph template for the new requirements in the 2016 Physics Syllabus. The major change is that max and min slope lines now need to consider all data, not just the first and last point.

You can download the updated version here but there are still a few issues (especially when you have data on the negative side of the x-axis). I'll be updating the file soon.