Question

Magnetic ceramics or ferrites contain compounds of iron. These have been used:
A: in panels for solar cells
B: as memory elements in computers
C: for building water-desalinators on ships
D: for making transformers

Answer 1

Hint: Magnetic ceramics or ferrites are electrically insulating. Ferrites are generally brittle, hard, iron-containing, generally black or grey in colour and are polycrystalline in nature. These materials exhibit a specific type of permanent magnetization known as ferrimagnetism.

Complete answer:
Ceramic magnets or ferrites are easy to magnetize. These materials are very resistant to corrosion and usually do not need any extra coatings for the corrosion protection. Let us discuss each statement given in options and find out the relevant use of magnetic ceramics.
Option A: Mono-crystalline materials are generally preferred to make panels for solar cells because mono-crystalline materials possess the highest efficiency and power capacity while poly-crystalline materials depict lower efficiencies. Thus, magnetic ceramics or ferrite being poly-crystalline in nature is not used in panels for solar cells.
Option B: Memory elements in computers known as memory chips are mainly composed of silicon, which is generally obtained from sand. Thus, magnetic ceramics or ferrites are not used as memory elements in computers.
Option C: Owing to the atomically smooth as well as atomically thin nature, graphene based desalination membranes or frameworks are generally employed for building water-desalinators on ships. Thus, magnetic ceramics or ferrites are not used for building water-desalinators on ships.
Option D: Magnetic ceramics or ferrites are highly responsive to magnetic fields for the low hysteresis losses, and moreover, these materials possess lower conductivity to reduce the eddy current losses. Such materials are required to make high efficiency transformers.

Hence, the correct answer is Option D.

Note: The most important features of ferrites or ceramic magnets include the high magnetic permeability as well as high electrical resistance. High magnetic permeability is mainly desirable in devices like antennas. On the other hand, high electrical resistance is mainly desirable in the cores of transformers in order to reduce the eddy currents.