Question

Why are the applications of permanent magnets in the field of engineering quite limited?
A: the field of these magnets are not everlasting.
B: they also lose their magnetism if they get subjected to physical shock or vibration.
C: their magnetic field is normally weaker.
D: all

Answer 1

Hint: A permanent magnet does not have any external power supply to maintain the magnetic capacity. The magnetic property is dependent on the orientation of charges and current within the material. A comparison of above properties with electromagnet would help us to find the right answer.

Complete answer:
Permanent magnets can be defined as objects which are made from a material that creates its own magnetic field, or as objects which gained the property of persistent self-generated magnetic fields.
Let us have a look at the options one by one, neodymium magnets are among the best and most efficient permanent magnets which were to be created. It is yet estimated that they lose about five percent of its magnetism every hundred years, unlike an electromagnet which produces a consistent magnetic field as long as it is powered up.
Though they do not require any external source to power them up in order to produce the magnetic field, the magnetic field generated by a permanent magnet is generally much weaker than an industrially used electromagnet. Also. Usually, to get a considerably good amount of magnetic field we would need a relatively huge magnet, but in electromagnet we can increase the amount of magnetic field by changing the orientation of the coil used, to form toroid and solenoid.
It has been experimentally verified that permanent magnets tend to lose their magnetic strength when subjected to physical shocks, breakage, vibrations and sometimes even excessive heat.
and thus, all these reasons are a cause for limited industrial applications of permanent magnets as electromagnets can provide much more strength which doesn’t deteriorate with time and can be controlled manually by changing the amount of current flowing through.

Option D is the right answer.

Note:
The magnetic field of a permanent magnet is caused by the action of an internal current and deteriorates with time. Permanent magnets don’t possess any dangers due to electric shock. Electromagnets magnetic fields can be turned off unlike permanent magnets.