Question

Why is the core of a transformer made of magnetic material of high permeability?

Answer 1

Hint : the permeability of a magnetic material is in a direct relation with the magnetism of a substance. A substance with higher magnetism can transfer magnetic fields more efficiently compared to a lower one.

Complete step by step answer
A transformer is generally a device used in converting voltages from one value to another. A transformer can be made in two ways, to either step down a voltage value or step it up. To step down a voltage means to change the voltage from a higher value to a lower value, thus reducing it. To step it up is to increase a lower one to a higher value. Also, only alternating current (or any form of a fluctuating current) can be stepped up or down by a transformer.
Usually, a transformer is made up of two sets of wires coiled around a core, one is called the primary coil and the other secondary coil. When alternating current flows through the primary coil, due to Biot-Savart law, from which it can be shown that a changing electric current induces a changing magnetic field, hence, this changing magnetic field can be felt by another turns of wire, and my faraday’s law, a changing magnetic field will induce current in a wire, hence this changing magnetic field felt by the second wire causes current to become induced in it. Thus even without contact, we have effectively conducted current from one wire to another. Now, these primary and secondary coils are usually coiled around a magnetic material made like a rectangular hollow to guide the magnetic field generated by the primary coil current to the secondary coil, so current can then be induced. The higher the magnetism of the material, the more magnetic field can be “transported” by it.
Since, higher permeability translates to more magnetism, so the cores are made with a substance of high permeability.
Hence, the core is made of a high permeability material to allow efficient transfer of magnetic field.

Note
For clarity, changing current in a wire can induce magnetic field due to Biot-savart’s law given as
 $\Rightarrow B = \dfrac{{\mu NI}}{{2R}} $ , where $ B $ is the magnetic field, $ N $ is the number of turns, $ I $ is the current in the coils, $ R $ is the radius. Hence, $ \dfrac{{dB}}{{dt}} = \dfrac{{\mu N}}{{2R}}\dfrac{{dI}}{{dt}} $ , when $ \dfrac{{dI}}{{dt}} $ is non-zero, then $ \dfrac{{dB}}{{dt}} $ exist.
Conversely at the secondary coils, by Faraday’s law.
 $\Rightarrow V = NA\dfrac{{dB}}{{dt}} $ where $ V $ is voltage or EMF induces, and $ A $ is the area of turns. Hence, if $ \dfrac{{dB}}{{dt}} $ is non-zero then EMF induced is non-zero.