Which of these components can be used as an electronic switch or amplifier? [T6B03]
Piece of cake this one is…. Lets go through the false answers first, just to make sure.
A. Oscillator. By definition, an oscillator simply takes a signal and, well, oscillates it. on/off, high/low, whatever. While definitely important in radio (you can’t get an alternating waveform without one) you can’t really make a switch out of one. It is possible to use an oscillator as an amplifier. It’s how vacuum tube radios get the work done (and that’s our first clue!)
B. Potentiometer. A potentiometer is nothing more than an adjustable value resistor. While it may have a switch built into it, such as an on/off/volume switch combination, a potentiometer by itself doesn’t make a particularly good switch. I suppose you could use it as one, by increasing a signal via the “pot” up to or below a given “cutoff” value…. but that’s a bit of a stretch.
D. Voltmeter. A voltmeter simply measures the voltage across a given circuit or component. Nothing more. It’s quite impossible to use one as a switch. (I think!)
So all that remains is C. Transistor. A transistor is a solid state device that toggles between states depending on an external input. By placing (for example) a 5V load on a transistor you can essentially “flip the switch,” and removing the voltage will turn it off again.