A-level Topics

Equilibrium of a Wall Shelf

This GeoGebra interactive allows students to vary the position of the centre of gravity of a shelf in order to observe the changes of the other two force vectors. The position of the supporting cable can be adjusted too.

The ability to resolve vectors allows students to apply principle of moments to understand how the vertical components of each force vary.

This is meant for the JC1 topic of Forces.

To embed into SLS, you can use the following code:

<iframe scrolling="no" title="Equilibrium of a Wall Shelf" src="https://www.geogebra.org/material/iframe/id/xdbr7qr5/width/700/height/500/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/false/rc/false/ld/false/sdz/false/ctl/false" width="700px" height="500px" style="border:0px;"> </iframe>

Pressure Nodes and Antinodes

I modified the progressive sound wave interactive into a stationary wave version.

This allows students to visualise the movement of particles about a displacement node to understand why pressure antinodes are found there.

Usually I will pose this question to students: where would a microphone pick up the loudest sound in a stationary sound wave? Invariantly, students will say it is at the antinode. When asked to clarify if it is the displacement antinode or pressure antinode, students then become uncertain.

According to Young & Geller (2007), College Physics 8th Edition, Pearson Education Inc. (pg 385), microphones and similar devices usually sense pressure variations and not displacements. In other words, the position within a stationary sound wave at which the loudest sound is picked up is at the displacement nodes which are the pressure antinodes.

For an alternative animation, check out Daniel Russell’s.

For embedding into SLS, please use the following code:

<iframe scrolling="no" title="Stationary Sound Wave (Displacement and Pressure)" src="https://www.geogebra.org/material/iframe/id/xbknrstt/width/640/height/480/border/888888/sfsb/true/smb/false/stb/false/stbh/false/ai/false/asb/false/sri/false/rc/false/ld/false/sdz/true/ctl/false" width="640px" height="480px" style="border:0px;"> </iframe>

Videos on Series and Parallel Bulbs

These are two videos that I made on series and parallel bulbs. The second video is specially made to highlight the increase in brightness of the remaining bulbs when one or more bulbs is removed from its socket.

What students will learn in O levels is that the brightness of the bulbs will not change as the potential difference is a constant, being the emf itself.

Based on the conflict between what is taught and what is observed, students will be led to discuss the reason why.

If anyone is interested in getting the demonstration kit, do check out Funlearners.com.

AC Power with Half-Wave Rectification

As a means of visualising what happens to the potential difference, current and power dissipated in an alternating current circuit with half-wave rectification, I have created the interactive applet with all 3 graphs next to each other.

It should be easy for students to see that with half-wave rectification, the power dissipated is half that of a normal a.c. supply with the same peak p.d. and current.