Question

Which of the following is not true about the advantages of electromagnet over permanent magnet?
(a) small electromagnets are used in electronic look
(b) scrapyard cranes have powerful electromagnets that lifts metal car bodies with ease
(c) magnetic resonance imaging machines use very powerful electromagnets to produce highly detailed images of the human body
(d) none of the above

Answer 1

Hint – In this question use the concept that there are only two categories of magnets namely permanent magnets and electromagnets. Electromagnets are special material that can be converted to magnets of any strength. Then think of the advantages of such a type of material over permanent magnets, this will help getting the right answer.

Complete step-by-step answer:

As we know that the magnets are of two types:
$\left( i \right)$ Permanent magnets.
$\left( {ii} \right)$ Electromagnets.
Permanent magnets
A permanent magnet is still magnetised, as the name implies.
Think of a kitchen magnet which has been trapped for years in a refrigerator trap.
Due to its permanent nature a permanent magnet can not be made so solid.
Electromagnets
Its magnetism only works when electric powered.

Advantages of an electromagnet:
$\left( 1 \right)$ They can be made stronger than any other permanent magnet.
$\left( 2 \right)$ These can be magnetized and demagnetized easily.
$\left( 3 \right)$ Increasing the amount of current increases the strength of the electromagnet.
$\left( 4 \right)$ Poles of an electromagnet can be interchanged by changing the direction of current.
Uses of electromagnets:
$\left( 1 \right)$ Small electromagnets used in an electronic lock.
$\left( 2 \right)$ Scraped cranes have powerful electromagnets that lift metal car bodies with ease.
$\left( 3 \right)$ Magnetic resonance imaging machines using very powerful electromagnet to produce highly detailed images of the human body.
So all of the above given examples are the uses of an electromagnet.
So this is the required answer.
Hence option (D) none of these is the correct answer.

Note – Commonly, ferromagnetic materials are used to create permanent magnets, an object once transformed into a permanent magnet can not lose its magnetism property, a north pole is named in permanent magnets and the other is the south pole. Popular permanent magnets are Alnico, samarium, and cobalt.