Using a microphone for salaah

Assalamualaykum Wa Rahmatullahi Wa Barakatooh
There appears to be no practical requirement for a microphone to be used for certain Salah in Masjid, in particular Fajr where, unfortunately, the congregation is small. Therefore I have 5 SPECIFIC questions:
Is it necessary from a Shar’ee perspective that the followers of the Imam need to hear the Qir’at of the Imam?
If the answer to the first question is in the negative, why are our Ulama using microphone for Salah?