Maglev trains move at high speed while hovering over the ground. No, there's no witchcraft involved; it's all science. Maglev is short for Magnetic Levitation. These trains don't have any engine. So how do they move? They use magnetic attraction and repulsion forces to float and go forward, to put it simply. Scientists have been working on the development and improvement of Maglev trains for over a century, but the first commercially used one was simply called 'MAGLEV' near Birmingham, UK and operated between 1984 and 1995.
I'm sure you know that in magnets, opposite poles attract and similar poles repel. Electromagnets are metallic coils that produce magnetic fields when current is passed through them, i.e. they become temporary magnets. These coils are placed along the guide-way of the trains, and large permanent magnets are attached on the underside of the trains. This causes a strong repulsion between the electromagnets and the train's underside magnets, and hence the train is levitated from the track to a height of about 10 cm.
An alternating current is passed through the coils in the guide-way. This causes the polarity of the electromagnets (i.e. north and south poles) to constantly flip, and not be fixed. But the polarity of permanent magnets on the train is fixed. So, the magnetic field in front of the train pulls the train forward, and the field behind pushes it in the same direction, thus causing the train to move forward at high speed. The polarities of electromagnets constantly change to cope with this mechanism. And to bring the train to a stop, the direction of current is changed, meaning that the magnetic field in front of the train repels it, and the field behind it pulls it, thus slowing the train down. This overall mechanism makes the Maglev train an efficient transportation system.
Moreover, it doesn't use any fossil fuel, and there is no friction between the track and train, so it has very low maintenance cost. It is also environment friendly, as it causes very little air and noise pollution, and uses power only when needed. Additionally, maglev trains are earthquake proof, and computerised, so accidents are minimal.
Albeit all the positive sides, the cost of building a wide network of maglev trains is really high. Currently, some developed countries like Japan, China, Germany etc. are using maglev trains. For a country like ours, maglev trains could be the ultimate solution to the traffic problems. Granted, it may take years to bring the technology to our country and it will be expensive, but who knows, maybe someday you can be the pioneer of Maglev trains in Bangladesh!