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1

You are correct, a cell phone antenna is bombarded constantly with radio waves from other phones, broadcast radio and TV stations, satellites, wifi routers ... it is a very long list. Several systems work together to single out the one signal meant for your phone. The antenna is an efficient receptor only for a narrow range of frequencies. Next, the ...


4

The motors like the one in your picture bear a lot of resemblance with primitive combustion engines. They require a push to start, and will keep rotating in the direction in which they have been pushed. They can only run smoothly if the rotor has sufficient inertia, if not, a flywheel must be added to increase it. And finally, they cannot run reliably at ...


11

A normal DC motor has 3 poles instead of just 2. This solves a couple of problems: the commutator doesn’t short out as it crosses from one pole to the other. the energized poles are always phased with the field magnets such that they never get in a place where they’re ‘stuck’. This Quora link has an animated illustration that shows the idea: https://www....


5

Inertia carries it through. I also think the brushes are arranged so only one slip ring can touch the brush at a time, otherwise you would get a short-circuit twice per rotation. Despite the image showing both slip rings touching the brush, the waveforms say different.


1

Look at examples of an AGC circuit Automatic Gain Control (AGC) circuits Theory and design paper or Understanding Automatic Gain Control Basically you need to sense the AC current with a sense resistor, amplify it and convert it to a DC value, the use a variable gain op-amp with a FET driven by the filtered DC value of the AC current to keep the AC ...


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