[SOLVED] What is negative voltage

[Genovator]

Hi people.....
Can anyone tell me in simple languages what is a negative voltage, how it is created and why it is used????

 

[shaiko]

First, you have to understand the concept of voltage.
Voltage is the scalar difference in electrical potential between 2 points in space.
If electricity was a "spring", voltage would be the "electric tension" between the 2 ends of that spring.


If you define the right side as the positive direction and left as the negative - straining your string to the left will mean that it's negatively strained.

 

[Plecto]

If you have a dual sided supply by simply connecting two batteries of equal voltage in series and calling the point between them ground, you will have both positive and negative voltage in referance to ground. When utilizing the negative voltage, the current will go from the negative side to ground, when utilizing the positive voltage, current will go from ground to the negative side.

 

[Genovator]

So, as per the concept, is the below circuit is valid????

 

[alexxx]

So, as per the concept, is the below circuit is valid????
View attachment 67353

Yes it is valid. You may see it in some different versions (no diodes or different capacitor values), but this is a linear supplier of +-15V.

When utilizing the negative voltage, the current will go from the negative side to ground, when utilizing the positive voltage, current will go from ground to the negative side.

Maybe I didn't understand well what you mean, so could you please elaborate? Current will flow from the most positive to the most negative point. From '+' to '-', or from '+' to '0', or from '0' to '-'. How can current flow from '-' to '0'?

 

[Plecto]

Maybe I didn't understand well what you mean, so could you please elaborate? Current will flow from the most positive to the most negative point. From '+' to '-', or from '+' to '0', or from '0' to '-'. How can current flow from '-' to '0'?

I just mistyped. I meant: "When utilizing the negative voltage, the current will go from ground to the negative side, when utilizing the positive voltage, the current will go from the positive side to ground"

 

[subbuindia]

I just mistyped. I meant: "When utilizing the negative voltage, the current will go from ground to the negative side, when utilizing the positive voltage, the current will go from the positive side to ground"

Hi friend.........

what is the significance of ground in your explanation?

 

[alexxx]

what is the significance of ground in your explanation?

Think of ground as 0V. Since current flows from the most positive to the most negative point, then '+' is more positive than '0' and '0' is more positive than '-'. Having this in mind, I believe you can now understand the way that the current will flow in the above cases.

 

[subbuindia]

Think of ground as 0V. Since current flows from the most positive to the most negative point, then '+' is more positive than '0' and '0' is more positive than '-'. Having this in mind, I believe you can now understand the way that the current will flow in the above cases.

Hi friend......

If we want to connect both nagative terminal and ground at a time, where we have to connect? I mean, in some times we are connecting negative terminal to ground. Then, in this case what is the difference between negative and ground?

 

[kak111]

Voltage is an electrical potential difference or electric tension between two points
— or the difference in electric potential energy per unit charge between two points
(denoted ∆V and measured in volts, or joules per coulomb)

In electrical engineering, ground or earth is the reference point in an electrical circuit from which other voltages are measured.
or in electric power grids a common return path for electric current, or a direct physical connection to the Earth.

Electrical circuits may be connected to ground (earth) for several reasons. In mains powered equipment, exposed metal parts are
connected to ground to prevent contact with a dangerous voltage if electrical insulation fails. Connections to ground limit the build-up
of static electricity when handling flammable products or when repairing electronic devices. In some telegraph and power transmission
circuits, the earth itself can be used as one conductor of the circuit, saving the cost of installing a separate return conductor.

For measurement purposes, the Earth serves as a (reasonably) constant potential reference against which other potentials can be
measured. An electrical ground system should have an appropriate current-carrying capability in order to serve as an adequate
zero-voltage reference level.
In electronic circuit theory, a "ground" is usually idealized as an infinite source or sink for charge, which can absorb an unlimited amount
of current without changing its potential. Where a real ground connection has a significant resistance, the approximation of zero potential
is no longer valid. Stray voltages or earth potential rise effects will occur, which may create noise in signals or if large enough will produce
an electric shock hazard.

The use of the term ground (or earth) is so common in electrical and electronics applications that circuits in portable electronic devices such
as cell phones and media players as well as circuits in vehicles such as ships, aircraft, and spacecraft may be spoken of as having
a "ground" connection without any actual connection to the Earth. This is usually a large conductor attached to one side of the power supply
(such as the "ground plane" on a printed circuit board) which serves as the common return path for current from many different components in the circuit.

(wikipedia)

 

[Plecto]

If we want to connect both nagative terminal and ground at a time, where we have to connect? I mean, in some times we are connecting negative terminal to ground. Then, in this case what is the difference between negative and ground?

Well, ground can be anywhere we wan't, it is just a referance point. If I were to make a virtual ground like in the top schematic in the image below, I could change resistors R1+ and R1- to let's say 100Ohm and 10k Ohm (to be extreme), this will make the supply +0.8V and -17.8V compaired to ground. I guess you could call the positive pole on a car battery ground if you connect it to the body of the car and run cable from the negative pole in isolated wires (I believe this has been done before), though it would be an unorthodox way of doing it

https://tangentsoft.net/audio/cmoy-tutorial/misc/cmoy-tangent-sch.pdf

The reason negative voltage is relevant is in IE. amplifier circuits. Sound is AC so the current will go in one direction and then change direction making a speaker element swing in both directions. Imagine if you had a resistor connected to ground between the two batteries in the first example and then connect the other end of the resistor to the positive end first and then the negative end, you will find that the current will change direction.

 

[alexxx]

Hi friend......

If we want to connect both nagative terminal and ground at a time, where we have to connect? I mean, in some times we are connecting negative terminal to ground. Then, in this case what is the difference between negative and ground?

As already pointed out by kak111, "Voltage is an electrical potential difference or electric tension between two points".
So if you have a 12V battery for example, this means that from the positive to the negative terminal, we have a potential difference between them of +12V (Vp-Vn=+12V). If you connect battery's '-' to a circuit's ground (0V), then the other terminal of the battery will be at +12V. If you connect the '+' of the battery to ground, then the other terminal would be at -12V (because 0-Vn=+12V=>Vn=-12V). Ground is a reference point. I believe that this term is confusing. If you forget the term "ground" and replace it with "0V", then you have a clear picture. Again "0V" is a reference point, this is why it suits us to give it a value of 0.

 

[Genovator]

Thanks a lot to everyone for their valuable replies.... I will soon post a schematic related to this topic for your comments and views....

 

[Genovator]

Hello everyone....
By your help and suggestions I had designed this circuit. It converts dc to ac (in both square and sine waves) and with the help of a transformer it can be boosted to 110 or 220 volts... Since I used TIP41C & TIP42C, so power dissipation is upto 65W.
Below is the schematic from the simulation and its resultant waveform....
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For square wave=>



For sine wave=>

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I hope it has no error.... If it has, then please rectify me....
Genovator