Foresight and Stability of Singapore Government

Its been a long time since I updated my blog.  Have been very, very, very busy......and was so guilty to take time off to update it.

Just attended the Singapore Science Teachers' Conference yesterday.  No, I am not less busy now....just a little tired....so decided to take a short break to write.

Had a very interesting talk by a NTU professor in Engineering who shared his insights on his wish list for skills he thought could be taught in Science in school.  Another thing he shared were some of the government projects he worked on.

I was amazed to hear that the Marina Freshwater catchment project's planning and feasibility study had come more than 20 years ago.  That implies that the project must have been started some time in the late 80's.  The government had worried about the constant threat of the expiration of the water treaty and the constant reliance on water on Malaysia and had been planning for steps on self-reliance.  Hence, projects like New Water and also Marina Barrage.  I also hear that to also remove reliance on power on Indonesia, the government had been looking at Nuclear facilities and other possibilities of cleaner power some time back and even before it made announcements in 2008 budget.

I know it sounds a little like propaganda and as if I am a little brainwashed but I cannot help but be impressed with our own Singapore government.

That brings me to a conversation I had with the Education delegates from Abu Dhabi and UAE when I was at a conference in UK two years back.  They had enquired how could our government accomplished so much in so short a time.

This is my interpretation.  We have very passionate leaders in power, people whom I believe fundamentally love the country, and will never want to see it fall.  We pay our leaders exceedingly well, so that there is no "excuse" for corruption, and in return the penalty for corruption is exceedingly high till you could possibly lose everything in your whole life and never pick yourself up again (I know it sounds cruel), but there is really no room for mistake.  So it is important to juggle this, cause you don't want the wrong people in power.

Politically, we are very stable.  I know some people do criticise the fact that we do not have a "alternative voice".  But the political stability is the other crucial factor, with the same party in power - they are able to make long term plans for Singapore.  10 - 20 year plan is not a problem and they know and will be confident that they will see it through.  Yes, I do agree that the occasional threats of opposition is good, it keeps our leaders on their toes, but it is definitely an advantage to have a stable group of people overseeing the growth. With long term stability, it is less likely to have leaders who are only concerned about what is in "their" portfolio when they are in term but can also have the capability to have projects that require long term implementation.

I guess that is what makes a key difference in Singapore. 

Similarly in the educational sector, we also see that many successful school are the traditional schools.  You have staff who are alumni, you have principals in power and who fundamentally see their school as their babies, you have people who care about the school and will see the school through both in times of highs and lows.  These are the people we want in service and want to make them stay in service.  Teaching is therefore not only a job it is a calling, a vocation.

Missing Energy When A Mass is Hung on a Spring?

Today we did a very interesting question in class.  The question goes something like this :

Consider a light helical spring that obeys Hooke's law.  Now, let us hang a mass m on the spring and gently lower the mass till the spring extends to an new equilibrium length.  If the net extension of the spring is e,
(a)  What is the loss in the gravitational potential energy of the mass?
(b)  What is the gain the elastic potential energy of the mass?
(c)  Compare the two answers, why are they different?

Most of the students who did this question, could easily deduce the answers to the first two parts

(a)  The loss in the g.p.e. was mge.  and

(b)  The gain e.p.e was 1/2 ke².  Now, from Hooke's Law, mg = ke.  Therefore gain in E.P.E can be written as 1/2 mge.

(c)  Comparing the two answers, we see that 1/2 mge went missing.....

Most students at this point in time would then ask two questions.  First, "Where did half the energy go to?"  the next is that "Is it possible to show that 1/2 the energy would be lost?"

• So let us try to tackle the first question:  Where did half the energy go to?

You see, this in fact a trick question.  We only considered the initial state and the final state without considering what happened in between. Consider if the mass as just hung on the spring and allowed to fall without any support.  At any point in time, there would have been two forces.  (Figure below)  The upward force by the spring T and the downward gravitational force mg. 

Initially, the spring is unstretched and the mass only experiences a downward force mg.  By Newton's 2nd Law, it would therefore also experience a downward acceleration and causes it to gain speed as it moves down.  However, as it stretches T increases and the acceleration becomes smaller.  Neverthless, before reaching the equlibrium point, it still has a downward acceleration and hence will still gain speed.  As it reaches the equilibrium point, T = mg.  Although net force is zero, it already has velocity and hence should continue to move down.  And as it has velocity at the equilibrium point, it also possesses kinetic energy.  And in fact 1/2 of the loss of GPE would hav been converted to E.P.E at that point. 

The trick in this question is therefore, the point that in reality the mass was "gently lowered" to the point of equilibrium and hence there should have been a 3rd external force acting on the system that is doing negative work on the system so that it dissipates the kinetic energy that could have been gained.

No, conservation of energy was not violated.  The loss in GPE was not all converted into Elastic PE of the spring as this was not a closed system, there was an external force acting on the system and it did negative work on the system, dissipating the rest of the energy.

• 
  
  The favourite question by my better students at this point would often be " Would you be able to further convince us that the work done by this force is exactly 1/2 mge as well?"

Remember, calculus is not a requirement in A-levels, therefore, not to deter my students with the Math, I decide to adopt the graphical approach.  (Though calculus is not required, they are expected to know

is area under the y vs. x graph.  Anyway, they have learnt this in their secondary school math as well.)

So we simplify the problem as such, consider that an external force F acts on the mass (e.g. like a hand) such that it applies a force in such way to lower the mass into the equilibrium so slowly that the mass may be considered to be moving at a constant rate and almost at rest.

Hence, there are three force T, F and mg on the mass m and F = mg - kx, where x is the extension of the spring. 

The work done by the external force F is therefore the area under the F-x graph. 

Now, from F = mg - kx.  The graph of F vs. x is a straight line graph, with y-intercept mg  and gradient -k.  Sketching the graph, and noting that at equilibrium, F = 0 and x=e.  We see that area under the F-x graph which is the work done by F is therefore exactly 1/2 mge. 

F acts in opposite direction  to the motion, and hence this work done is actually negative and it seeks to dissipate the kinetic energy that could have been gained.

Hope this answers the question!

Interesting Video : Newton's Dark Secrets

 

Newton's Laws of Motion together with the study of dynamics forms the foundations of classical physics.  The A-level syllabus and hence the school dedicate alot of the time, especially in the first year in teaching of Mechanics.  My students are always facinated with Newton, his discovery of the three laws and then the Law of Gravitation.  They had also earlier, in their secondary school studied on Optics, where they read about Newton splitting the light into its various colours.  Usually students who do Physics will also do Math and also encounter Newton - Rhapson Method in the approximation of roots.

This "Father of Classical Physics" has therefore also astounded my students with his discoveries.  Sometimes I like to add a little twist to my lessons and therefore, if I have the time, I always like to show this video to my students as it forms a nice ending to especially the study of Mechanics.  My students are always surprised to find that Newton was afterall very human and had weird habits (having an obsession of alchemy and also trying to calculate the end of the world).  Though this video does not show the best side of Newton, it shows his passion and thirst for knowledge had also interest my students to find out more about other Physicists.

A Useful Site for Teaching College Physics: The Physics Source

Today I would like to feature this website known as the "The Physics Source".  It is a featured by Compadre which is also another site which contains very useful resources for students, teachers and faculty members.  However Compadre is a very large site that contains many, many, many other references to sites, so I will rather review each one as I come across.

I particularly like this site as it contains many materials particularly suited for teaching introductory College Physics.  As there are many topics that are also taught in A-levels, the materials can be easily adapted for a A-level classroom.

All the resources are already classified thematically e.g. mechanics.  Under each theme the resources are further classified topically.  Once you enter into the topics, you will have a view of the available resources.  Beyond the title of the resource, there is a brief description on what each resource is and also the weblink to get the resource.

This will definitely be a website I will be visiting see what are the resources available for the topics I am teaching or lecturing.  This is so exciting!

Waves in the Sky - Wave Clouds

[Picture Source:  Compliments of Mr Ong Jek Yaw, 2010]

In the teaching of waves and standing waves, we often use the ripple tank to illustrate phenomenon associated with waves.  Today, I learnt something from a very experienced colleague of mine (Mr Ong Jek Yaw).  In reality, we have an extra large "ripple tank" in our sky!  The rows and rows of clouds that form the sky are in reality known as wave clouds, and they are formed when the atmosphere is disturbed and a "gravity" wave travels through.

From what I understand, wave clouds are form when a thin and stable layer atmosphere is disturbed, e.g. when it passes over a mountain.  The air disturbance can propagate like ripples in the pond when the stone hits the water.  As the wave moves through the air, it undergoes repeated uplift and descent. If there is enough moisture in the atmosphere, clouds will form at the crests of these waves. In the descending part of the wave this cloud will evaporate due to adiabatic heating, leading to the characteristic repeating cloud/clear bands. (wikipedia)

Stationary waves form in the atmosphere can also result in structures observed as well.

Two particularly interesting wave clouds video can be found on youtube and are embedded below:



[ Video above from Youtube, by akrherz at http://www.youtube.com/watch?v=yXnkzeCU3bE]

[Video above from Youtube by RobyF5  at http://www.youtube.com/watch?v=Dvl3PrXwBkI&feature=player_embedded]
More about wave clouds can be found in the links below.

http://www.weatherquestions.com/What_causes_wave_clouds.htm

http://www.theweatherprediction.com/habyhints/64/

http://en.wikipedia.org/wiki/Wave_cloud

http://weathervortex.com/sky-ribbons.htm

Winplot - My Favourite Graphing Software! It is FREE!

In the teaching of physics, it is often that we need to do plots of equations. Many A-level teachers tend to use Excel. This is great when I am creating questions which requires students to take points off graph grids, however, not so great when I just want general (but accurate) shapes to different graphs.

My search of a software became imperative when I was lecturing waves and wanted to generate many different sinusoidal graph starting at different phases. After plotting a few graphs on excel, I gave up and decided to ask a (Further) Math teacher, who told me that she used a free software Winplot.

I have since been using Winplot to generate all my graphs. I found it relatively easy to use for generation of graphs - just type in the equation and the software auto generates for you. You get the flexibilty to change the scale set the thickness and it can be easily copied to the clipboard which can be pasted in any Word document.

It has been almost 7 years since I found Winplot and am still using it. The author constantly makes improvements to it and it is now one of the most powerful graphing software and the great thing is it is still FREE! It is also relatively easy to pick up and there are many external "instructors" that have produced tutorials, manuals, and video instructions.

If you are looking for a free graphing software, this is definitely one to try out.

Most updated version can be found at : http://math.exeter.edu/rparris/winplot.html

A good startoff point for learning are a set of instructional video by Steve Simonds which can be found here : http://spot.pcc.edu/~ssimonds/winplot/

Other supplementary materials can also be accessed here: http://math.exeter.edu/rparris/wpsupp.html

There are some youtube videos as well, one of which is given below.  If you like them, you can google for more at youtube.

A Resource for Teaching Semiconductors: The Solar Cell

An Introduction to Solar Cells

Phys. Teach. 48, 306 (2010)

http://link.aip.org/link/?PHTEAH/48/306/1

[Picture from: http://www.sxc.hu/photo/1054612, johnnyberg, The essens of summer]

The study of Semiconductors and explanation of its behaviour by band theory was introduced into the H2 Physics Syllabus in Singapore for A-level Physics in 2006. Generally, for this topic we learn the mechanics of it, but so far there has been little exploration of its applications in real life.

The May 2010 issue of the Physics Teacher (see link below) carries an interesting article on how solar cells work. It explains the workings of it using band theory as it is a semiconductor. It should find great relevance in today with environmental issues becoming a pressing problem that the world faces.

The link is listed below. I would like to explore how to further apply this article to classroom teaching and integrate this into the A-level syllabus, either as a reading for an activity that can enthuse students or even as an examination question.
The abstract is quoted below:

Abstract : (©2010 American Association of Physics Teachers)

"Most likely, solar cells will play a significant role in this country's strategy to address the two interrelated issues of global warming and dependence on imported oil. The purpose of this paper is to present an explanation of how solar cells work at an introductory high school, college, or university physics course level. The treatment presented here will be qualitative and somewhat simplified, in order to reach the desired audience; references are provided for a more detailed and mathematically sophisticated treatment. It is hoped that this paper will, in a small way, motivate students to learn more about this technology, so critical to the energy and environmental future of this country. "

Why a smaller sphere having a smaller charge can have an electric field that is stronger than a larger sphere having a larger charge?

This is a followup post to my previous post on the misconception that a smaller spherical conductor will have a larger charge and hence there is a greater possibility of it being discharging.

I did the same question with another of my class today.  However, this time, this class of students had more problems in visualising why a smaller sphere having a smaller charge could possibily have a stronger electric field at the surface.  I also had students who told me that their secondary school teachers told them that it was the charge per unit area that mattered and asked me how to reconcile this with the concept of electric field being stronger.

Let us address the first issue first.  To aid in the visualisation.  I drew the following picture.  In this case, we had already made a calculation of 0.3 micro-coulomb on the small sphere and 0.9 micro-coulomb residing on the larger sphere.  So if there is one electric field line drawn for each 0.1 micro-coulomb charge on it sphere, then we see can have:

So from the diagram above, we see that the although there is less charge on the smaller sphere, the electric field lines could be closer, and hence the E-field could be stronger.

Now for the second question, was the secondary teacher right in saying that it is the charge per unit area that mattered.  Two ways to understand this, first the diagram shows fundamentally an essential point in drawing field lines, the no. of field lines are proportional to the charge, therefore have a greater no. of charge per unit area, essentially means more electric field lines per unit area and hence the field lines will be closer and in other word, the electric field is stronger.

Alternatively, those who prefer to see equations will have 

From the equation, we can see that the electric field strength at the surface of the charged sphere can be written as a constant multiplied by  (Q / surface area of sphere), so essentially the secondary teacher who relates the electric field at the surface to the Q per unit area is actually correct.

A Common Misconception: More Charges Accumulates on a Sharper Point...Is it Really True?

[Picture Source: stock.xchng, "Raw Power1" (2008) by gun4fire]

When I was an O-level student, I was often told by my Physics teacher that as more charges tend to accumulate on a point that is sharper and hence there is a greater likelyhood for discharge and therefore, lightning rod are built to be sharper.  As a typical O-level student, I was like my student now, and just readily accepted what my teacher said then.

While teaching electric field at A-levels, we have a typical problem whereby we have two spherical conductors in which we connect a "long" wire across them.  We then place a certain amount of charge onto the system and the charges with redistribute till they come to electrostatic equilibrium.  (A similar problem can be found in Serway's "Physics for Scientists and Engineers"(6th Edition), Problem 25.50, pg 791.)

After the calculation, we may find some interesting results.  The electrical charges collected on the larger sphere are in reality more than that of the smaller sphere.  However the electric field at the surface of the smaller sphere is large.  The electric field represents the force acting on per unit charge, and hence logically the larger the force the higher the probability of discharge.  Hence I guess, the idea of more charges accumulating at a sharper point and hence greater probability of discharging, can be quite misleading....


PS:  This article is a followup on a previous comment contributed which triggered this idea.  It is possible to start off with the Windhurst machine activity and then follow up with the problem above and a discussion of breakdown voltage.

Problem 25.50 in Serway (6th Edition), pg 791:
Electric charge can accumulate on an airplane in flight.  You may have observed needle-shaped metal extensions on the wing tips and tail of an airplane.  Their purpose is to allow charge to leak off before much of it accumulates.  The electric field around the needle is much larger than the field around the body of the airplane, and can become large enough to produce dielectric breakdown of the air, discharging the airplane.  To model this process, assume that two charged spherical conductors are connected by a long conducting wire, and a charge of 1.20 micro-coulombs is placed on the combination.  One sphere, representing the body of the airplane, has a radius of 6.00 cm, and the other, representing the tip of the needle, has a radius of 2.00 cm.  (a)  What is the electric potential of each sphere?  (b)  What is the electric field at the surface of each sphere?

Popular Science Archive is now free!

My husband and I have always enjoyed Popular Science magazine, and used to be a subscriber till my magazine vendor stop carrying it. It is a great magazine targetted for the layman as it introduces in plain language what are some of the technologies that people are recently developing around the world. Occasionally, I can come across interesting reads that I can use in my lessons.

Good news for all! Recently, Popular Science are partnering with Google to make available their 137 years of archival magazines Popular Science and Popular Mechanics. You can find the archive at http://www.popsci.com/archives.

Or alternatively, you can get both Popular Science and Popular Mechanics in Google Books! I hope this is a trend for magazines to come.

A Greater Need to Build the Hands On Skills of Our Children

I had a nice gathering with a bunch of present and ex-colleagues of mainly Physics teachers and was discussing about the practical skills of our present day students. We all shared the same sentiments, the hands-on skills of our students have declined over the years.  We had stories of students who were not able to strike matches, students who did not know how to tie a simple pendulum - they said that they never tied shoelaces as their track shoes came with shoe laces tied and their parents or maids would tie it back for them after the shoes are washed.  There were students who could not handle drills, and almost drilling their hands when by using the hand to hold a wooden stick directly below the hole to drilled.  Students who also had problem using saws and hammer and would be terrified when given the tools.

These are the group of students, who spent their childhood at home playing with toys, computers or drilling on homework.  They had a different childhood from many of us teachers,who did not have access to computers which only became a common household item when we were in university or when we were working.  We had spent our childhood playing with neighbours, running around in the neighbourhood, building structures to have war games (though I was a girl, I was always following my brother and engaging in the activities he was involved in).  During mid autumn festival, we had lanterns or some made lanterns from pomelos peels, tin cans which we lighted candles in. For me and my friends, we also spend quite alot of our teenage years, fishing, camping and also staking out in abandoned kampungs with durian trees to wait for durians.  Alas, what a childhood we used to have.  It is no wonder, the kids do not have the hands on ability to build or handle apparatus in Physics experiments.

I shall resolve that my children will not be like that and I feel that the hands-on practical work should have a greater emphasis not only in the Secondary and Pre-university school years but also starting at a very young age.  Children should be exposed to various activities that require them handle tools, build things.  Performing the experiment and getting them to just infer or deduce results, which many schools are doing are just not sufficient.  You must literally do the work, get "dirty", handle the tools to acquire the dexterity for more complex work later.

Useful Tool for Drawing 3D - Google sketchup

I was at the Times bookstore last Saturday as it was my birthday month and I wanted to spend away 20% discount card.  I came across a new free tool called Google Sketchup.  It is tool that allows for drawing of 3D diagrams. 

I think that it will be a useful tool for Science Teachers.  If you do a google on sketchup, you can also find many free models for sciences available through the internet.  I have not learnt how to use it yet, but will definitely get to loading and using it.

The tool is available for download at http://sketchup.google.com/

Setting Exam Questions - Beyond Bloom's Taxonomy

  Most JCs are in the midst of setting their prelim questions and promotional examination questions at this time of the year. This is no different at my college, last Friday a colleague who is new in teaching came and seek me advice on how I usually set questions and he asked me if it was alright for a question to contain many different parts on a story line. So, we had a chit-chat and I shared my experience on setting questions with him, in the midst I realised that it may be possible to pen down some of experiences and hopefully, some new teachers can benefit from it.

Usually each examination will have a specific table of specification (TOS). For each question and topic that I am assigned to I have something similar as well. Usually, I will go through the syllabus and identify all the concepts that I need that students to be able to show mastery in. I usually start off by setting the structured question first, unless I have just come across one very particularly good question in MCQ. For the structured question. as I set each part of question, I check off the concept that has been tested. This avoids over testing of one particular concept - as each mark in the paper is very precious. It also alerts me to which other the concepts that have not been covered in the examination. That allows me to set an appropriate question in MCQ to ensure that concept has been tested

Many schools also use the Bloom's taxonomy to guide them. However, I find that a little difficult to use at times especially in physics were almost every question is an application and applications and extrapolation can be both difficult and easy depending on the question. However, I find it useful to follow the following:

(i) I usually start setting the main scenario of the question. For beginners, a good point is always to pick an interesting question from past questions, or a textbook question. I then first solve the question. Usually textbook questions especially the more challenging ones will need to be solved in parts.

(ii) Then I add in parts to the question for ensure that students are guided to achieve the final answers, start off with the easier calculations and slowly lead the students in. There should not be more than two steps in each part.

(iii) Revisit the question, look at if there are any appropriate qualitative questions that can be added in to get the students to explain a new scenario if something in the questions is changed or if what is calculated can be placed at the end of the question. Sometimes, if there are more than sufficient marks to play with I will also get students to sketch graphs pertaining to scenario, this helps to extend students' thinking and also assess students' ability to translating information to abstract representations.

(iv) When the bulk of the question is set , I then assign the marks for each part. (We will talk more about how I assign marks below) Usually each setter is given a certain of marks to play with for the question to be set. For the filling the rest of the marks, I will now go back and place some regugitative questions like definitions to the front or intermediate parts of the question. For example in a gravitation question on dealing with force approaches that utilises Newton's Law of Gravitation, I would put in a "State Newton's Law of Gravitation" in front. If an energy approach is needed later, I may add in the definition of Gravitation Potential Energy of a 2 mass system. This is particularly essential to guide the students' train of thought in examinations.

4. Throughout the whole process, be clear of the learning objectives that you wish to set, this especially important in awarding of marks. For awarding marks in the question, I make sure I tie the points in my question to a particular concept that I wish to illustrate. So beyond just writing down 1 mark - I usually have a remarks column in my own marking scheme to note down also what this one mark is for e.g. illustrating knowledge of application of Newton's Law of Gravitation.

5. From the description of 3, I also note that beyond just setting a question. I do take note that in all my questions, there should not only be just calculations. In all the questions I set for a topic, I always ensure that there is a little bit of regugitative work (10 - 20% of question), a little bit of calculation (30% -40% should be something familiar), more calculation (10% - 20% more challenging), some graphical work (20%) and some qualitative explanations part (20%) -both of which usually proofs to be more challenging for students.

6. Back to the question on whether it is appropriate to have many different scenarios in a question. It depends on how many marks is allocated and what the objective is for the question, for some time is needed for the candidate to explore and understand each new scenario. For example, in the case if we are looking at a synthesis question on how students understand conservation of energy is applied throughout the various topics in Physics, then each part could be description of a different scenario like describing the energy changes that occurs in a spring undergoing simple harmonic motion, a block sliding down a slope, the excitation and de-excitation of an electron when a photon is incident on it etc. Each scenario is however short and familiar. However, if the scenario could be something not familiar and a lot of description is needed to get the students into the story line, then it makes no sense to give a new scenario every two parts. E.g. in the case where Tarzan swings and picks up Jane and swings back again. The scenario should be sufficient to present itself with many questions the setter can set for. Having a new scenario for each one or two marks is very unfair to the candidate as there is in fact more time needed for candidate to truly understand the scenario.

Quantum Mechanics Conceptual Survey

My friend sent me a research paper on Quantum Mechanics Conceptual Survey (QMCS).

The QMCS is a survey to assess students' understanding of quantum mechanics and is intened to be used to measure the relative understanding of quantum mechanics.  As with the most conceptual tests used for research, the authors have protected the security of the test by keeping it from becoming available to students.  After administering the test, they do not post solutions or allow students to take the tests home.  They have also administered it online but on a password-protected enviroment with warnings to students not to distribute it.

Instructors or Physics teachers interested in obtaining a copy can request copy at http://per.colorado.edu/QMCS.

My Role as a Teacher in Physics

  To me, the point about Physics education is not just dishing out the facts and expecting the students to do well. I always emphasize to my students, that it is an intriguing subject, because it forces you to learn how to learn, and it forces you to think at different perspectives. Physics is a subject that trains its learner to be logical. Many a times, the exact problem is not even formulated into an equation for your to solve yet. You need to read, interpret, make reasonable assumptions and model the situation to something solvable. Beyond that, you need to have a good grasp of mathematics to be able to tackle the problems. Getting the answer is uninteresting. You must be able to interpret the answer to your calculations, give conceptual understanding to it and then explain in a coherent manner to your peers your interpretation (so some mastery of language is needed). Furthermore, you must try to internalize what you have learnt to put into new context. Isn't this what real world problem solving is about?


  As teachers, I feel that we must therefore be aware of training skills beyond just the academic knowledge, many of our students will not in fact take on physics, JC is the time they are exposed to the rigour of various subjects and through them they learn more about themselves and will go on to further pursue their interests. Learning how to learn in new situations, from various information, is a more important lifelong skill they can apply for the rest of life.

  This is also why I find that putting students in teams that they have not worked with is important. The world has globalised.  Even as a teacher, I find that the soft skills of negotiation, teamwork, conflict management, socialising etc. are important. With the complexity of many real-life tasks, you need not only be competent in knowledge at workplace, but possess the necessary skills to both lead and work as a team player.

  Preparing students sufficiently for their future....isn't this what teaching is about?

Tips in Lecturing 1 : What to look for in The design of Slide.

Preparing my lecture slides for gravitation and my husband is overlooking my shoulders.  He says that " You have nice slides...maybe you should document some tips for lecturing."  Okay...so here I share some things I take note of when I design my slides, in case I forget.

1. 
   
   Ideas on each slide must be clear.  Have only sufficient words to allow you to recall what you want to say.  Point form is great....students can read notes....and they should be encouraged to study from notes and texts. 
2. 
   
   Put the concept that you want to say on the title.  Keep to one concept per slide, too many concepts the student may miss the point.  Only use more than one when you need to review previous concepts or do a consolidation at the end.
3. 
   
   Also put the reference to the lecture notes or textbook on the slide title.  This allows the students to refer to the elaborations when they review the slides.
4. 
   
   Make it aesthetically appealing.  Highlight key words in bold and colour.  Add a diagram, photo when possible.
5. 
   
   Check your font size is sufficiently large to be ready by your last row of audience, you can check it with students in the first lecture and make adjustments.  Usually I keept to trebuchet at least a font size of 20. I avoid Times New Roman cause the words tend to too thin.
6. 
   
   When developing arguments I tend to rehearse what I want to say when I design my slide and animate the points when they come out.

Yap that is it for now.....will write more when I think of more.

US satellite to monitor debris

US satellite to monitor debris (Click on this link to access the article.)

Source: Straits Times
Date: 4th July 2010

This is a great article to include during the teaching of Gravitation. Students learn about how satellites are launched, and are often taught that they will continue to spiral inward as they lose gravitational potential energy and gain kinetic energy and eventually burn up in atmosphere.

However, in reality, we do leave a lot of debris and trash in space and now we are causing problems for ourselves.

A lesson in National Education perhaps? Though not directly related to Singapore, but relates to character development and the care of the environment, and our responsibility as inhabitants of the earth.

Software Recommendation: Dia - A Free Software To Draw Circuit Diagrams

Dia :  A Free Visio-like Software

In teaching electricity, there is always a need to draw many circuit diagrams.  I had initially used the Art box in Microsoft Word to draw the diagrams.  However, I found it a little cumbersome as constant adjustment of the diagrams are needed especially linking between the different circuit components.

I was introduced to Microsoft Visio and I do admit it is useful, but too much an overkill for me as it is relatively expensive considering the fact that I only want to use it draw electrical diagrams.

Recently, I came across a free, open-source software called Dia.  It is a great software, as it contains most of circuit components that you can easily find in the A-level syllabus.
It is a slightly scaled down version of Visio, but definitely serves my purpose.

This is a definitely a good tool to have with you.

[Click on the title of this writeup to access the site to download the software.]

Examination Tip #1 : Useful Stationery to Have - Customised Self-Inking Stamp

  This is strictly not a physics post....but rather a post for all students.  I noticed when invigilating many tests and examinations,  that students spend alot of time writing their name and index no. on every sheet of writing paper that they wish to hand in.  (At least they bother.)  This allows for any pieces of paper that could easily come lose from the stack during the transportation (esp. when you are sitting for internation examinations and scripts get sent from place to place) to be easily traced back to the "owner".  However, it is very tiring especially when you attach more than 10 sheets of writing paper, I had a case where the student attached 20 sheets for the Math paper and ended up writing till he complained that his hands ache.

  One very useful tool to acquire is a Self-inking Rubber Stamp which you can customise what you put on the stamp.  Put your name and centre no./index no. on the stamp.  Use that to stamp across every writing paper you are using.

Recommended Textbooks for Advanced Level Physics Part 3 : United Kingdom Text - Advanced Level Physics by Nelkon & Parker

Textbook Reviewed :  Advanced Level Physics (by Nelkon & Parker)


This was the classic text used by most Singapore schools at the time that when I was still a student.  The current edition is much better than the 6th Edition, which I felt the paper was so thin that I was so afraid to tear it.  It is still one of the key British texts that I constantly refer to, maybe I was familiar with the lay out.

What I Particularly Like About The Text:

This is a text particularly suited for the A-level syllabus.  It contains much information especially on experiments that students particularly need for the A-level examination.

I always recommend this as a reading text for my students, as I find it helps the students to hone the way they write  (in a scientific manner).  Language and arguments are done in a formal manner and it does improve the quality the students write.  Since the A-levels are set by UK examiners, it is best to understand what the examiners are saying.  This helps in understanding of the questions set in the A-levels examinations as well.
  
This is also a good text as it covers everything and also beyond the A-level syllabus, which is good as A-levels do expect the student to be informed beyond the syllabus and provides good grounding.  (Btw, the O-level text - "Principle of Physics" is particularly good...helped me score my distinction in Physics when I did my O-level....was utterly grateful for it.)


What I feel needs to be improved:

The same with all other British texts, I hope to see a version of text with :

• more colour
• highlighting of the more important points in boxes esp. the essential definitions and explanations.
• Layout can be more friendly and aesthetically done
• More pictures (hopefully colourful ones)
• Have scaffolding questions before dumping the students with the examination style questions which are nevertheless important.

Recommended Textbooks for Advanced Level Physics Part 2 : United Kingdom Text - Advanced Physics by Tom Duncan

Textbook Reviewed:  Advanced Physics by Tom Duncan

This is another textbook which I commonly refer to when I prepare for lectures and tutorials. 

What I particularly like about the Textbook:

Explanations are very detailed and clear.  Definitions are again very precise.  I also particularly like the detailed descriptions and well-labelled diagrams of the experiments and all essential experiments are given.  The drawings were often traditional clipart drawings which you could easily duplicate for exams using your pencils, unlike the diagrams nowadays in US texts which tend to replace them by real objects and students may not know the skill to draw the schematic diagrams which they need to produce in examinations.

Areas that can be Improved for the textbook:

  I was first exposed to this text when I was an A-level student - this was the other recommended text besides Nelkon and Parker.  However, I found it a little difficult to follow as the concepts and ideas were not introduced in the sequence taught by my lecturers or tutors, this was further complicated by the fact that the tutors did not point out specifically where I could refer to for each chapter of the text.  To give you an example, for the study of thermal physics I had to look at one chapter for the various bonds of the materials to see how they affected specific heat capacity and another chapter for example on gas laws.  Examples in the texts were also too few and so I found it difficult to scaffold  my learning and found it difficult to apply what I have learnt to the questions given for tutorials.  So eventually, I still stuck on to my Nelkon and Parker.  As a teacher, I got around this problem, as I was familiar with the instructional objectives of each topic, so I usually search for the information I need through the glossary, e.g. suppose I was looking for information on Conservation of Energy, I would then go to the glossary and read through all the relevant pages on Conservation of Energy.

 As usual, end of chapter problems were usually UK A-level examination questions,  therefore they pose difficulty to a student new to the topic as there was too great a jump from the concepts to the application of concepts to exam-style question.  It would have been better to have some simpler questions that were first relevant and arranged according to the concepts introduced and then the slightly more difficult ones that were more at the examination level, and then finally the examination style questions.

[Note:  Diagram is taken of http://www.amazon.co.uk/.  In the case that anyone wishes for me to remove it I can easily do so.]

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Recommended Textbooks for Advanced Level Physics Part 1 : United Kingdom Text - Physics by Robert Hutchings

Somehow, after 3 months into the Pre-university Physics course, many students would find themselves struggling in the course and approach the tutors for a recommended text.  We usually make a list of a few texts that we use but till date for the Singapore curriculum, we do not have a single text that can satisfy the needs of the Singapore A-level Physics.  As teachers, we ourselves refer to a few texts.  My suggestion is therefore as such.  Pick a textbook that you find readible....you may want to start off borrowing from the library and use it for a few chapters, see if you find it easy to read and understand. before buying it  Supplement with other textbooks from the library when needed.

In this series I will look at a few textbooks that I use in my teaching and preparation of lecture notes and my comments on them.

Basically, there are two types of textbooks that I use - the British Textbooks for A-levels and the US Textbooks. 

The key strength of the British Textbooks are:

• They are very targeted towards the A-levels.  Afterall, the Singapore A-level Physics students are sitting for the Cambridge paper.
• The language is written in a very British style, which is rather formal and precise.  Reading them helps to hone the skills in writing scientifically in a formal manner.
• The definitions are very precise, much more in my opinion to the US texts.  Therefore, they are the key source when I need to look for definitions to put in my lectures.
• There is great emphasis on the experiments that verifies the laws and concepts.  So detailed descriptions with setups are given.  This is great for design experiment questions when sitting for the examinations.
• Contains end of chapter questions that are from the UK examination board.

The key thing that puts me off is the organisation.  Somehow, it may not be very readible, lines after lines after lines of words which you have to go back many times to understand.  Many books are also monochrome with little diagrams and diagrams that are in black-and-white do not appeal to me.  Questions are usually just examination style questions, they do not scaffold learning and are usually not arranged in a manner which follows the sequence the concepts were introduced.

Book 1: Physics (Bath Advanced Science) by Robert Hutchings

This is the textbook that many Physics tutors would refer to for definitions especially when there are disputes amongst ourselves on how much is needed in the definition.  It can a simple argument as to whether "gravitational field strength can be defined as force on a unit charge", which by the way is not accepted by many tutors - it should be "force per unit charge" which conveys a different meaning.

It is mainly the key text as Hutching has been one of the Chief Examiners for the Cambridge A-level Physics paper that Singapore students have been taking for many years.

The book was first published when I was a student and I could not fully appreciate the text.  After reading the topic I often found it lacking in sufficient depth nor scaffolding enough for me to attempt the tutorial questions given to me.   

However, one particular advantage that this text had over others were that there was almost a Data Analysis (DA) question at the end of every topic.  At that time the DA question was relatively new, and very and almost no books carried them and yet we were to be assessed.   For those of you not familiar with what DA questions are, they are questions that gives a set of real life information of and allows you to make analysis on the relationships.  The question itself is very long with alot of information given as figures, charts graphs and the students are given a set of questions which they are expected to decipher and pick out only the relevant data to solve the question at hand.  Questions are very authetic e.g.  apply Conservation of Linear Momentum to the various ball games like cricket, tennis, golf etc.

As a teacher, this is still the key source of reference which I go to for definitions and DA questions.  I have learnt to appreciate some of the intermediate examples set by Hutchings e.g. the long question (which I think contains part (a) to (j)) on the use of indicator diagrams in gas law...doing that question alone helps student really familiarise with the use of First Law of Thermodynamics and the different thermal processes like isothermal, isobaric and isochoric processes.

Difference Between Electric Field and Electric Field Strength

To put it simply, the electric field is a region of space in which when a charged object is placed in the field.  It will experience a force acting on it.

However, in Physics, we would prefer a more specific way to define a quantity, and as with gravitational field, we would like to have a definition that allows us to quantify a physics physical quantity.  Hence, we assign an number (and also a direction) to every point in the field.  In this way, we can find out about the force acting on the charge placed at the point in the field if we were to know the charge and the field strength.

The electric field strength is a property of the field and not charge placed there.  Hence, we define the electric field strength at a point in an electric field as the force acting per unit charge on a small positive test charge when placed at that point in the field

Electric field strength at a point in field, E =  F/q

where F is the force acting on the charge q placed at that point in the electric field.

This equation not only defines for us the magnitude of the field strength at a point, but also the direction of the field.  Although the definition specifies a positive test charge, in practical test of the field, we can always use a negative test charge, the q will then be negative.  What it simply means is the field would be in opposite in direction to the force experienced by the negative test charge.

Students also often ask why there is a need to have a small test charge.  This is to ensure the that the test charge itself does not distort the original field significantly. 

Bargains for Members at AAPT

The American Association of Physics Teachers (AAPT) is having a great booksale for their members. Just choose 5 books for the price of USD 30 (excluding statement), maybe that is sufficient motivation to entice me to renew my membership....I stopped renewing when my school subscribed to "The Physics Teacher".

If you are interested, you may go to http://www.aapt.org for more details

Why is there a need for the concept of Gravitational Field?

  A few students have been coming to ask me this,"Why is there a need for the concept of gravitational field? What is its significance?" They have been quite happy to accept Newton's Law of Gravitation and could not see a need for the concept of field.  So I will try my best to discuss this to my best understanding.
  When the concept of gravitational force was discovered, there was a great disbelief by many scientists of that age and one of the key question faced by the scientists then was "How could 2 objects without touching each other have an effect (force of attraction) on each other?"
  I always jokingly tell my students that this is because they have never seen Chinese kungfu and experience qi gong, or watched those martial arts Chinese serials....but back to the point.....
  To overcome this obstacle for understanding, the concept of field was then created.  Any object which possessed mass (let us call it a source mass) would be able to exert a field around itself (its like having invisible arms of influence).  Under normal circumstances, we would not be able to see the field.  However we know that a field is there when we place another (test mass) in this field as we can see that this test mass will experience a force.
  For physics, we like to quantify properties.  So we would like to quantify this field by the source mass.  Now, we would expect that the larger the value of source mass, its gravitational field should be larger.  (compare that of Earth and Sun) The further we are from the source mass, the less influence the source mass should have on the test mass. The gravitational field can only be "seen" by the test mass, but yet is a property of the source mass, hence, we measure that force that is on the test mass by the field, but divide that force by the test mass so that we have a quantity that becomes independent of the test mass
 
  The gravitational field strength at a point in the field, g = (Force on a test mass placed at the point)/(test mass)

If the source of the field is a point mass M, then we can further write g = GM/r^2
, where M is the mass of the source mass, and r is the distance from the source mass.  This is consistent with our argument above.

Hence, a gravitational field is just a region of space in which a mass when placed in it will experience a force and the force experience by the mass m placed is equal to the product of the field strength at that point and the mass of the test mass placed there.

 

About Me

I am a Physics Teacher teaching in a Junior College in Singapore. Physics was not my first choice of teaching subject, rather I was coerced into it. But I had a privilege of meeting some very inspiring Professors when I was in NTU/NIE and found it very fascinating and intriguing, in the end when I was asked to make a choice between offering Mathematics or Physics in honours, I chose Physics and have not ever regretted my choice. Eventually graduated with a first class honours in Physics and was the Lee Kuan Yew Book Prize Gold winner for my graduating batch.

I am now into my 12 years of teaching Physics, and the subjects still fascinates me. As I teach, I learn, especially when my students ask me questions and seek to answer them in a way that can allow them to understand the answers conceptually. With this blog, I hope to pen down my experiences in Physics which can include, questions that are asked by my students, books that I have read, interesting websites that I have visited and anything to do with Physics as well as my teaching of Physics.

Further points about me:

Schools that I have taught in :

• Hwa Chong Junior College (1998 - 2002)
• Meridian Junior College (2002 - 2006)
• NUS High School of Mathematics and Science (2006 - 2007)
• Hwa Chong Institution (College Section) (2008 - Present)

My Interests :

• Physics and the teaching of Physics
• Educational Technology (Any technology that can enhance learning)
• Cooking (Find my food blog at http://foodexpt.blogspot.com)
• Research (Tentatively looking at using cooperative learning in the teaching of H2 Physics at Junior College Level)