Question

Name the material of core in electric bell, electromagnet, d.c motor, a.c generator and transformer.
A. Soft iron
B. Hard iron
C. Soft steel
D. Hard steel

Answer 1

Hint:A magnetic core is a high-permeability piece of magnetic material used in electronic, electro-mechanical and magnetic equipment such as electromagnets, transformers, electric motors, generators, inductors, magnetic recording heads, and magnetic assemblies to confine and direct magnetic fields. It is composed of iron-like ferromagnetic metal, or ferrimagnetic compounds such as ferrites.

Complete answer:
A coil of wire around the centre that holds a current is also generated by the magnetic field. The existence of the core will raise the magnetic field of a coil over what it would be without the core by a factor of several thousand. The use of a magnetic core will concentrate the power tremendously and maximise the influence of the electric currents and permanent magnets generated by magnetic fields.
The properties which a good core should have are:
-The magnetic core's geometry.
-The sum of the magnetic circuit air gap.
-The properties of the central material, such as hysteresis and permeability.
-The core's operating temperature.
-If the core is laminated in order to eliminate eddy currents.
Soft iron core is utilized to make magnetic substances as its profit and losses magnetism rapidly rely upon the presence of magnetic fields. The armature is additionally made of soft iron which can initiate magnetism quickly. Since soft iron satisfies all the conditions it is used as a core.

Hence, option A is correct.

Note:Although soft iron is used in all magnetic devices but it is quite rare and expensive. So, things like iron nails are used. Soft iron is ferromagnetic in nature and consequently which helps in reinforcing the magnetic field lines in the centre as the quantity of the lines are increased in the centre. This is useful in expanding the sensitivity of the moving coil galvanometer.