IP4 11 Current Electricity

03 February

Rheostat Simulation

Seng Kwang Tan IP4 11 Current Electricity 0 Comments
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A rheostat controls the size of the electric current by changing the resistance in a circuit using a resistive track and a movable slider. Moving the slider changes the length of the resistive path, so a longer path gives a larger resistance and smaller current, while a shorter path gives a smaller resistance and larger current.

This morning, I was watching my students conduct an experiment with a rheostat and saw a few of them connecting the two lower plugs (A and B as shown in the simulation). I had to explain to them why the current would not change no matter how they move the slider. Then it occurred to me that this could be best explained using a simulation. So I created this simple simulation using a little vibe-coding to help my students visualise current flow through a rheostat, hopefully preventing them from connecting it the wrong way.

I used the following prompt on Trae.ai: “Create this html simulation of a rheostat. The canvas should show a realistic image of a rheostat with its three plugs. One above, next to the rod on which the slider is resting. Two on either side of the coil of wire. The user can connect two wires to any of the three plugs. The simulation should show the direction of current flow, from one terminal out to the other terminal. The resistance value will then be shown. Make the maximum resistance 20 ohm.”

It produced a working prototype within one prompt. I then made further prompts changes to refine the app. Trae.ai makes fast iterations much less painful as it only makes the changes to the necessary codes without having to generate the whole set of codes from scratch.

For Singapore teachers, this simulation is optimised for SLS and is directly embeddable to SLS as my github domain is whitelisted. Just paste the URL (https://physicstjc.github.io/sls/rheostat/) after clicking “Embed website”.

Rheostat simulation
Screenshot of the rheostat simulation

05 December

Simulation of electron drift speed versus temperature

Seng Kwang Tan 15 Currents, IP4 11 Current Electricity 0 Comments
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Metal Lattice Simulation

3.0 V
20 °C
Mean drift speed: 0.0 mm/s
At low temperature, ions vibrate less, so collisions are fewer and drift speed (and current) is higher for 3.0 V.
Your browser does not support the HTML5 canvas tag.

This simulation demonstrates the principle that the resistance of a metal conductor increases with temperature. As temperature rises, the metal ions in the lattice vibrate more vigorously. This increased vibration causes charge carriers (electrons) to collide more frequently with the ions, hindering their movement. As a result, resistance increases and the current flowing through the conductor decreases for the same applied voltage.

At the A-Level, this simulation extends the understanding of current by examining it from a microscopic perspective in terms of mean drift velocity. Instead of viewing current simply as the rate of flow of charge, students learn that electrons in a conductor move slowly on average, with a small net drift in the direction of the electric field. The current depends on how many charge carriers are available and how fast they drift. This is expressed using the equation:

$$I = nAv_dq$$

where II is the current, nn is the number density of charge carriers, AA is the cross-sectional area of the conductor, vdv_dis the mean drift velocity of the electrons, and qq is the charge of each carrier. As temperature increases, more frequent collisions reduce the drift velocity, helping to explain why current decreases even though the charge carriers are still present—linking microscopic behaviour with macroscopic electrical measurements.

12 September

How to survive a lightning strike

Seng Kwang Tan 15 Currents, Blog, IP4 10 Static Electricity, IP4 11 Current Electricity 0 Comments

This is an interesting question on electricity: in order to survive a lightning strike, which of the following costumes offer the best protection? A coat of armour, your birthday suit, a wetsuit or a superman costume? Watch this MinuteEarth video on Faraday’s cage to find out!

30 April

Squishy Circuits

Seng Kwang Tan 15 Currents, IP4 11 Current Electricity, Teaching Resources 0 Comments

image taken from http://courseweb.stthomas.edu/apthomas/SquishyCircuits/howTo.htm

I came across this Ted video on Squishy Circuits, presented by AnnMarie Thomas from the University of St Thomas and found it to be a suitable activity for kids. I shall attempt to make some when I am free with instructions from the following site:

http://courseweb.stthomas.edu/apthomas/SquishyCircuits/index.htm

Be sure to watch this page for photos and videos!

As I was contemplating the potential of combining conductive and insulating dough to make fun toys with the help of electric motors and the learning that can come from it. Apart from the obvious learning related to electrical resistance and current, we can even learn about flotation and fluid dynamics by building floating boats of different hull shapes.