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Showing posts from January, 2015

Frogs Levitate in Strong Magnetic Field

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Some things like iron nails are known for their magnetic properties, but why should frogs levitate in a magnetic field? The trick is to get the magnetic field right – you can’t just use any old bar magnet to make a frog levitate.

Frogs, like everything around and inside us, are made up of millions and billions of atoms. Each of these atoms contains electrons that whizz around a central nucleus, but when atoms are in a magnetic field, the electrons shift their orbits slightly. These shifts give the atoms their own magnetic field so when a frog is put in a very strong magnetic field, it is essentially made up of lots of tiny magnets. And there’s nothing special about frogs. All materials – including strawberries, water and gold – are ‘diamagnetic’ to some extent, but some are more convenient to levitate than others.

Frogs are convenient not only because they have a high water content, which is a good diamagnetic material, but also because they fit easily inside a tube-shaped Bitter ele…

Have you ever been on a train going through a tunnel or a plane and your ears pop? Why does this happen?

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A: Inside your ear there is a pocket of air. This pocket is normally at the same pressure as the air outside your ear to help you hear, but if the air pressure around you changes, you feel the air pushing on your eardrum. Your ear has a small tube for equalising the pressure between the inside and outside of the ear that is opened when you swallow and when the pressure is equalised you often feel a pop.

In a plane, the high altitude means the air is thinner and although planes are pressurised, the air pressure is still much less than on the surface. This difference in air pressure can be felt by the ears, particularly on takeoff and landing when changes in altitude make the pressure difference happen more quickly.

The train in a tunnel is slightly different. When the train enters the tunnel it squeezes the air in front of the train creating high pressure in the cabin and you sense this change in pressure.


There are some ways to equalise the pressure between the inside and outside of …