Question

The material used for making the armature of electric bell is
A. aluminum
B. soft iron
C. steel
D. bronze

Answer 1

Hint: Recall the construction and working of the electric bell. Check the properties of that the material of armature should possess to get used in the electric bell. Check the magnetic properties of the materials given in the options and compare them to the standard properties that the material of the armature of electric bell should possess.

Complete step by step answer:
-The armature of the electric bell needs to show magnetic properties only when it its magnetized otherwise behave as a non-magnetic material.This means that the material used for making the armature of the electric bell should magnetize quickly as the electric current pass through them and de-magnetize quickly as the electric current stops.
-The aluminum is non-magnetic in nature in normal conditions. But it is an example of paramagnetic material. Also, it doesn’t get magnetized or de-magnetized quickly. Hence, cannot be used in the electric bell.Hence, the option A is incorrect.
-The steel is highly magnetic in nature and does de-magnetize quickly. Hence, steel cannot be used in an electric bell.Hence, the option C is incorrect.
-Bronze is also non-magnetic in nature, so cannot be magnetized. Hence, it cannot be used in electric bell.Hence, the option D is incorrect.
-The soft iron shows weak or temporary magnetic properties. When the button of the electric bell is pressed, the circuit in the electric bell closes and current starts flowing through it.Due to this current, the armature of the electric bell made up of soft iron gets magnetized, hits the gong and bell rings. This bell rings as long as the current flows through the circuit and stops quickly as the current flowing stops due to de-magnetization of the soft iron in the armature of the electric bell.In such a way, we get the electric bell ringing only when the button is pressed ON and stops ringing when the button is OFF.

Hence, the correct option is B.

Note:The students may think that the aluminum is paramagnetic in nature. So, it should get magnetized when electric current flows through the circuit of the electric bell. But the aluminum needs more than that flowing in the electric bell circuit to get magnate. That’s why aluminum is not used for making the armature of an electric bell.