What is the ruling on transferring microphones and electrical appliances from one mosque to another to benefit from them in the new mosque, given that the previous mosque no longer needs them?

It is permissible to move an endowment from its place if its benefit there has ceased, so long as the relocation does not lead to the cessation of the endowment's intended purpose. Therefore, there is no harm in moving microphones and electrical devices from the old mosque, where they are no longer beneficial, to the new mosque, which is in need of them.