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What energises the secondary of the Transformer?

Jamie asks:

“I am told that no magnetism escapes from a transformer due to the closed loop. If that is the case, what is energizing the secondary winding?”

MAGNETISM : Why repulsion is told to be the test for magnetism?

Sreeda sked:

“Can a magnet lose its magnetic properties?How?
Why ‘repulsion’ and not ‘attraction’  is suggested to be a good test of finding whether a substance is a magnet or not?”


A magnet can lose its magnetism.

A magnetic substance is made a magnet by making the molecules which are individually possessing magnetic properties align in a particular direction. In the unmagnetized state they are arranged randomly and hence do not have magnetic behaviour.

If a magnet is heated, beaten, mishandled etc, it will lose its magnetism.

Why repulsion is the sure test for magnetism?

A magnet can attract the opposite pole of other magnet as well as the magnetic substance (iron cobalt nickel). SO, if A magnet attracts another object, we cannot say that the other object is a magnet. But if the magnet repels the object, then we can surely say that the other object is a magnet. Because “Like poles of a magnet repel each other”

A question from Magnetism

Rishi asked:

“It is said that an iron piece behaves as a magnet when an external magnetic field is applied. Then otherwise why doesn’t it behave as a magnet even though the earth’s magnetic field is acting on it.”


Every molecule of iron possess magnetic behavior. But in the absence of an external strong magnetic field, the individual molecular magnets form closed loops or they are arranged in a random fashion in such a way that the net magnetic effect is zero.

Since the magnetic dipole moments of all the molecular magnets inside the iron add up to zero, the iron rod does not respond to earth’s magnetic field like a magnet.

Further, the strength of earth’s magnetic field is not so large to magnetize a piece of iron. The coercivity of iron is also very less (it can easily lose any acquired magnetism)

However, steel buried in North South direction is found to acquire some magnetism.

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April 2021

Schrodinger’s Cat in Daily Life

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