Electromagnetism rocks!

This place could bring out the twelve-year old in you.

It was an apartment near the heart of Coimbatore; where each room was filled not with occupants and their household items, but shopkeepers selling various technical and industrial goods; and I was in one of these…shop-rooms. Outside the lone window, a passenger train occasionally roared past, setting the window-glass clanging and resonating. But the outside world hardly mattered now.

Here, in this shop were loads of curious things. Solar goggles to view sunspots and eclipses. Squat and ornate microscopes. Black binoculars, their lenses shimmering.  Various science experimental kits of your choice – barometer making kit, optics kit, aeroplane modelling ones, and more. A couple of rolled-up posters, partially revealing awe-inspiring Hubble pictures.  Most of all, large gleaming telescopes that could zoom you across the universe to the glorious rings of Saturn or the  island universe of Andromeda. I had been to this place once before, two years ago now, to buy my first refractor. And now it already felt more familiar and homelier than home itself.

It is hard  to become a twelve year old again, to re-learn all the things you had once learned at school with fresh vigour. Well, if you ever had wanted to do that, you had come to the right place. Smiling like someone who had just got a hundred birthday gifts, I returned home with a good electromagnetism kit.

It’s great fun actually, there is loads of science behind the whole thing; and I could hardly have waited more to buy the kit and blog about it. If you hate to be reminded of your school textbooks, that is fine. But I hate memorising a fat physics book as much as you probably do. With our present messed-up education, it is hard to convince people that they are not actually doing science unless they are getting their hands dirty with hands-on experimenting. Anyway, here are some stuff done with the kit.


Iron filings sprinkled over a sheet of paper, below which there is a ring shaped magnet.  The filings get attracted, and arrange themselves along the direction of the magnetic lines of force.


Same as above, but with two ring shaped magnets below the paper. The two magnets have unlike poles facing toward you…so it is North-South or South-North.


This pattern is formed using the ring magnet by placing the neutral, curved face beneath the paper; with the north and south poles to the left and right. This is also the pattern you would get with a bar magnet.


The two magnets with opposite poles facing each other, with iron filings between them in a bottle; revealing three dimensional magnetic lines of force. You could almost see the magnets trying to get to each other, almost like they were parted lovers or something.


Once, it was thought that electricity and magnetism were separate things. This changed forever when in the early 1800s a guy named Oersted noticed that a compass needle when placed near a piece of current carrying wire showed a deflection. Later, others like Ampere, Faraday and Maxwell would investigate the intimate relationship between current and magnetism. Here, the circuit has a battery and a tightly wound coil of copper wire, called a solenoid. From what I remember after reading Resnick-Halliday’s Fundamentals of Physics a year or so ago, the coil creates a magnetic field along its axis whenever a current passes through it, making the compass needle deflect along that direction.  In short, we have just made our first electromagnet. Still don’t believe that the coil is now a magnet? Get a load of this:


We see our helpful iron filings again. Recognise the pattern formed here? Duh…! It is basically no different form the pattern due to a bar magnet. The strength of the electromagnet of course, depends on the strength of the current passing through it; and the north-south polarity depends on the direction of the current.


Now we see Mr. Solenoid again, with a compass below it and two ring magnets with opposite poles facing each other to the side. So what’s up with this decorative arrangement? Basically, in a crudest way possible, we have made a galvanometer – a device for measuring current. How? The solenoid creates a magnetic field along its axis. The ring magnets create another magnetic field along the left-right direction, perpendicular to the previous. The compass needle does a sort of compromise, and comes to rest in an intermediate position between both fields; leaning a bit more to the stronger of the two fields. Thus, if there were no current, the needle comes to rest in along the field of the Ring magnets, toward the 0 degree mark on the compass. For larger and larger currents, the needle comes to rest along the direction of the coil, toward the 90 degree mark. The deflection is a kind of measure of current. Crude, but effective.


Combining all the concepts above, we could make a DC motor, a device for converting electricity into action. Here, we have something similar to the solenoid (here it is called an armature) that is able to move round an axis; which is surrounded by a magnetic field. When there is a current in the armature, it becomes an elecromagnet and comes to rest along the field caused by the surrounding magnets. The trick here is to reverse the direction of current when this happens (to interchange the magnet’s polarity), so that the poor armature is forced to move further to come to rest in the opposite direction, only to find that the current has been reversed yet again when it had achieved this…and so on….the armature keeps moving till the current runs out. Of course, there is no big deal in changing the whole thing to a DC generator – just remove the battery to a galvanometer or some device which requires electricity; and spin the armature manually…the galvanometer shows the deflection.

Did I ever tell you that…electromagnetism rocks?

Thats it for now. All my thanks are to Skypoint, the place where I bought my first telescope and regained…my lost childhood.  If you ever happen to visit Coimbatore, try to pay the place a visit. ( address/phone no?) It is not everyday that you come across a shop dedicated to science.

The Descent of the Phoenix

I’m probably the last person on earth to blog about this picture, but it is amazing. Like, wow.

This sweeping image was taken at the Red Planet by NASA’s Mars Reconaissance Orbiter. In the black and white colours of this photo, we see a large 10 kilometer wide crater – a memory of an impact by a meteor that took place perhaps a very long time ago. Even as the huge scale of the impact is easily apparent, there is an even more amazing thing in this picture…the Phoenix lander descending, it’s parachutes unfurled to slow down the amazing speed with which it descends, and battling the immense pressure with the thin Martian atmosphere. So we have, in the vast unkown of the Red Planet, a piece of machinery designed by intelligent life to gather vast sums of knowledge about it, photographed by another piece of machinery from the same intelligence, orbiting the planet three hundred kilometers away.

From this two-dimensional photo , it looks as though the spacecraft is falling straight towards the crater itself…but actually it is falling to a place ten kilometers in front of it. This fact really makes us grasp how high the spacecraft, and how huge the crater in the background is. Once the spacecraft lands, it will commence on a search for liquid water, headed by optimistic humans who wonder whether conditions are suitable for life only on Earth , trying to answer the age-old question…”Are we alone?”

Janus is here

Here’s some science to think about for the new year. Now the earth moves round the sun once in a year. The earth’s axis is tilted at an angle. Here is the thought – Suppose you go out everyday at the SAME time and mark the position of the sun as a dot in the sky throughout the year with an imaginary pen…You would get exactly 365 dots. So how would the 365 dots look like? Would all the dots crowd together in the same place, making it a single dot? Or would they form a random smattering of dots, roughly in the same place? Would they form any specific curve, like a circle or an ellipse?

Normally you’d expect that the sun’s position on a specific time will be the same throughout the year, but things are not so simple. The earth spins around itself not erect, but at a tilt. That’s why the sun rises earlier in summer than in winter. The tilt is what causes the seasons. So the first option definitely isn’t the answer.

The motion of the earth around the sun is periodic – it repeats itself once in 365 days, so you should expect something that loops itself every year to be the answer. In fact, the dots form a perfect elongated figure “8” called analemma- something that makes weird sense for this new year.

The top and bottom ends of the ‘8’ correspond to the summer and winter solstices, and the center corresponds to the equinox . You could make something like a sundial with this idea – Take a stick, fix it and note the shadow of the stick at the same time everyday (or every month – you would still get the outline of an 8) and mark the month. I made a crude one by taking readings at 12 o’clock every month….


I took the pic on Jan 1st 2008, 12 noon. See the shadow pointing toward ‘January’?

Here’s my idea of a new year greeting card. 🙂


Sorry for the high resolution…didn’t have time to shorten it.

Janus is the Roman god of gateways and openings, of beginnings and endings…that’s why January is named after him. Again, wish you a happy new year.