Author Options:

Voltage is still a little confusing? Answered

I'm a little confused about voltage, it's the electrical "pressure" i know, but what is the purpose of lowering the voltage? What happens if the voltage is too much? Wouldn't adding resistors to change the amps have the same effect?

3 Replies

lloydsteve0 (author)2018-01-24

Most components are designed to withstand up to some specified voltage. Even when there is no current flowing. For example a MOSFET may have a Breakdown voltage (yes that's what it is called) of 100 volts. Exceed that and guess what? it breaks down. That may not destroy it though. If the power supply can deliver a large current in excess of the MOSFET's maximum then it can certainly become very hot very fast, then it becomes a short circuit and then it explodes.

Limiting the current by using resistors is not much help unless that is the purpose of the design as the resistors will also get very hot depending on the voltage and current and the power rating of the device. So even with the MOSTFET turned off if the voltage is too high and it starts to conduct current due to breakdown then you have no control of the circuit. Either use a higher voltage rated MOSFET or redesign your power supply to prevent this. The same can be said of other transistors except that when their voltage is exceeded it is generally fatal as they turn to short circuits and may also explode if the power supply has the ability to do so.

Select as Best AnswerUndo Best Answer

randofo (author)2017-11-09

I am not sure I understand your question. In what context are you talking about raising or lowering voltage?

If you are asking why things work at the voltage they do, that is a larger question that I am not sure I can satisfactorily answer for you.

Resistors in and of themselves don't change the voltage.

Select as Best AnswerUndo Best Answer

TimothyS40 (author)randofo2017-11-14

Lowering voltage lowers costs. You will not need to build your device as robustly, saving on components, and if your device is battery powered the batteries last longer.

Too much voltage, say 20 V, on a device designed for lower voltages, 5 V, causes component degradation/failure. It might not happen right away but it will happen.

Yes, adding more resistors will give the same effect but that costs more in components and needs more space for the intended design.

Select as Best AnswerUndo Best Answer