## Variable Resistor Simulation

My third simulation in as many days. This time round, I created some png files for electrical circuit components that can be used for future simulations. I also figured out how to add text in line with a variable in the drawing panel for the simulation, hence the units can now follow the values of the meter readings.

## Simulation for Potentiometer

Continuing the course on Easy Java Simulation, I did this simple simulation on the Potentiometer, which allows students to first predict, and then verify the position of a jockey to achieve null deflection of a galvanometer.

Click on the image below to try it out and do give me your feedback. I’ll try to improve it with whatever little skill I have.

I decided on a DC circuit simulation as I could not find many on Open Source Physics EJSS platform. With this as a template, I guess I can develop more simulations on the same topic when I have time.

## Vertical Throw with Free Fall Simulation

This is a simulation done from scratch after attending a crash course on EJSS. It displays the velocity and acceleration vectors as an object is projected vertically upward with a uniform downward acceleration. The initial upward velocity can be altered using a slider. The graph of velocity is traced as the ball moves.

https://physicslens.com/ejss/verticalthrow_Simulation.xhtml

## Getting Tides Right

I was reading up on tides this morning as I have to relieve a colleague’s IP2 class on forces, when I stumbled upon this video. It explains tides in a way that differs from most textbooks that clarified for me why the oceans bulge at both ends along the Moon-Earth line at the 2’30” mark onwards.

## Stirling Engine

I bought a simple beta Stirling engine online at dx.com recently and it came in the mail today. It works well with a cup of hot water placed under it, although it might take a little push to get it started due to the initial static friction. However, once it starts spinning, the wheel goes on and on for a very long time.

From the video, you can observe the expansion of the air within the main piston cylinder as the heat below raises the temperature and pressure. This forms the power stroke. When the piston rises, it pushes air into a secondary piston, which also helps to provide torque to the wheel. When the air in both pistons expand, it cools down. An understanding of the 1st law of Thermodynamics (JC syllabus) is necessary to appreciate why that happens. Upon cooling, pressure decreases and the pistons fall. The cycle repeats itself.