What is the voltage difference between positive and negative voltage?

Answer 1

The sign determines the direction of flow of electrons. This matters for direct current appliances and most things with computer chips in them, since memory storage, logic chips, diodes, LEDs, etc require current from one direction to operate. AC however, varies from positive to negative voltage sixty times per second (in the US- 60 Hz) which allows the power to transmit further distances through powerlines than DC would allow.

Additional Answer

It's important to understand that 'voltage' is another word for 'potential difference'. You cannot apply the terms 'positive' and 'negative', in the sense of 'polarity' or 'charge' to a potential difference or voltage. You cannothave a 'positive voltage' or a 'negative voltage' in this sense.

'Positive' and 'negative', in the sense of polarity or charge can, however, be applied to potential. For example, you can say that an object has a "potential of +100 V or -100 V" with respect to another object. What you cannot say is that there is a potential difference of +100 V or -100 V between the two objects.

The key to understanding this is that 'voltage' is another word for 'potential difference', NOT 'potential'. So you CANNOT have a 'positive or negative voltage' because we cannot have a 'positive or negative potential difference'.

We can, though, apply the terms 'positive' or 'negative', in the sense of 'direction' to potential difference (or voltage). For example, we could arbitrarily apply a 'positive' direction to a voltage which acts clockwise around a closed loop, and a 'negative' direction to another voltage which acts counterclockwise around the same loop.

So you need to sort out in your mind exactly what you mean by 'positive' and 'negative': charge (or polarity) or direction? And then re-phrase your question.

Answer 2

positive volts are voltages that are positive with respect to ground (zero volts). negative the same but only the voltage is lower than ground (zero volts). Sometimes you need both positive and negative voltages when dealing with analogue devices. Say you want to convert an analogue signal to digital. the process is called A to D conversion. since analogue is bi polar (as a sine wave goes pos and neg over and under zero as does music, radio waves, etc) you would need both pos and neg voltages to measure the positive and negative swings of the analogue signal. it is much easier to do that than it is to convert the signal using a pos or neg voltage as a reference baseline.