besides discussing the answers to yesterday's question set, mainly talked about two cases here..
a loudspeaker uses an AC motor.. alternating current meng.
it goes like this.. the speaker slots into a round magnet, with north in the middle, and south around it. when a current is put through and around the thing, it pushes the speaker out.. and when the current switches (AC) it comes back.. the vibration causes sound.
to increase volume (aplitude) the current would be turned up.
to increase pitch (frequency) the frequency would be turned up.
the other case sues a DC motor, a galvanometer (or ammeter)
its got the same structure as a regular DC motor, but there is a spring with produces tension, which prevents the arm from continuously spinning. the more current that is put through, the higher the force, and thus the further the needle points.
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