Transistors are useful in equipment such as hearing aids and small radio receivers because transistors ?
Hint:Transistors are small electronic components with two main functions.They connect as a switch to control circuits and they can also amplify weak signals. The transistor is in almost every electronic device we use. Let us understand this device in detail.
Complete answer: Transistors are made of semiconductors such as silicon. Each silicon atom is bonded with four neighbouring silicon atoms. Silicon has four electrons in its valence shell. Each one of these electrons goes for sharing with a neighbouring silicon atom and forms a covalent bond.The electrons are in their valence band. If the pure silicon has to conduct electricity. The electrons have to absorb some energy and become free electrons. Thus, pure silicon will have a low electrical conductivity.
A technique called doping is used to improve the conductivity of semiconductors. Doping is the injection of foreign material to enhance the performance. For example, we can inject phosphorus with five valence electrons and as the phosphorus gets injected, one electron will be free to move in the system. This is known as n-type semiconductor because electrons(negative charges) are moving and conducting the current.
Similarly,if we inject the semiconductor with boron which has three valence electrons. Now, this creates a hole, a place where there should be an electron, but there is not. It still increases the conductivity of the silicon because electrons can move into these holes.Although it is the electrons that are moving, we usually say holes are moving around. And since the hole is the lack of an electron, it actually acts as a positive charge and this is why it is called a p-type semiconductor.
Now that we have understood the basics of transistors, let’s answer the question, they are useful in equipment such as hearing aids and small radio receivers because transistors present in them amplifies or increases the volume of sound. Transistors are incredibly tiny and can easily fit in the plastic package worn behind the ear.
Note: A transistor is made with both n-type and p-type semiconductors. A common configuration has $n$ on the ends with $p$ in the middle and this is called an NPN transistor.A voltage or current that is applied to any pair of the terminals of a transistor controls the current through the other pair of terminals.