15 September

Make Your Own Comic Strip for Teaching!

Seng Kwang Tan Blog, Teaching Resources 0 Comments

A concept cartoon is an innovative way of eliciting discussions about science concepts. For example, it can present differing views on a scientific phenomenon from different characters.

I am not an artist but do wish sometimes that I could make classroom discussions more interesting by using relevant cartoons or comic strips. Then I stumbled upon some websites that enable you to create your own comic strips using readily drawn characters and images. The characters have a number of common facial expressions, which makes the story-telling fun. You may even add on your own colours or drawings such as backgrounds and other objects later on after you have downloaded the soft copy of the image for the strip that you have made.

Do try out http://www.makebeliefscomix.com/Comix/ where I made a strip as a trial. I certainly hope to get more ideas for teaching in future where this will come in handy.

Free Concept Cartoon Generators

12 September

How to survive a lightning strike

Seng Kwang Tan 14 Current of Electricity, 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!

01 September

Newton’s Nightmare

Seng Kwang Tan 18 Electromagnetic Induction, Demonstrations, IP4 16 Electromagnetic Induction 0 Comments

This demonstration is called Newton’s nightmare because it involves the slow dropping of a magnet that seems to be inconsitent with gravitational acceleration.

Using the “CFILE” structure, we can explain how the magnet moves much slower in a metal pipe than when it is undergoing free fall (as in the PVC pipe, which serves as a control).

Now, the metal that we use cannot be ferromagnetic, or the magnet will not even drop at all. It will simply be attracted to the pipe and stick to it.

However, if another metal such as copper or aluminum is used, as the magnet moves through the pipe, different sections of the pipe will experience either a change (either decreasing or increasing) in magnetic flux. Sections of the pipe that the magnet has just gone through suffers a decreasing flux while those that the magnet are approaching gains magnetic flux.

By Faraday’s law, which states that an induced emf is proportional to the rate of change of magnetic flux linkage, emf and hence, current is induced within the pipes. These induced currents are called eddy currents.

By Lenz’s law, the induced currents tend to flow in a way so as to oppose the change causing it. The current in the sections of the pipe that the magnet is leaving will trying to attract the magnet while those that the magnet is approaching will try to repel the magnet.

The effect is that the magnet experiences a retarding magnetic force that acts against gravitational force, hence decreasing its downward acceleration.

01 September

Diamagnetism

Seng Kwang Tan 16 Electromagnetism, Demonstrations, IP4 14 Magnetism 0 Comments

I didn’t want to spend money on buying a piece of pyrolytic graphite and large neodymium magnets so I made do with what I have to make the following video. While diamagnetism is not in the A-level physics syllabus, it’s good for students to know that there are other classifications of magnetic materials.

What we study in our syllabus is ferromagnetism, which is exhibited by materials such as iron, cobalt and nickel. Some pencil leads are paramagnetic (weakly attracted to magnets) while others such as the one in the video are diamagnetic (repelled by magnets).

I bought my neodymium magnets from DX.com and the shipping to Singapore takes about 3 weeks, so you might want to factor that time in if you want to get some for your lessons. These magnets are great for other demonstrations such as homopolar motors and Newton’s nightmare.