Actually, what is this Virtual Ground concept?

Virtual Ground Analogy

Look at this circuit Diagram.

Virtual ground appears in the common point between two series connected resistors, if

• two voltages are applied to the other ends of the resistors,

• they have opposite polarities,

• they bear the same proportion as between the respective resistors.



Virtual ground phenomenon is summing of opposite equal quantities, which is associated with continuous energy wasting.

Virtual ground point represents the result of summing two opposite and usually equal quantities.

Virtual ground is not only a "mystic" electronics phenomenon that we can observe only in op-amp circuits with parallel negative feedback (op-amp inverting circuits). 

It is a unique worldly phenomenon that we can observe in many situations of our human routine where we solve problems in a wasteful and extravagant way - by continuous wasting of additional energy.

Here are a few funny examples revealing the philosophy behind this great idea.

We may observe the virtual ground phenomenon in many situations of our routine when we - especially being lazy and, at the same time, rich enough:) - solve the problems by continuous wasting of additional energy.

Analogies:
Thermal. Assume you keep the temperature in your room at 20° C (this is your thermal virtual ground). Now imagine that you have broken a window; as a result, the temperature in the room begins dropping (if it is winter) or rising (if it is summer). What do you do? Obviously, you have to repair the broken window. But if you are too lazy and, at the same time, rich enough:), there is another strange solution to retain the desired temperature. You can turn on a heater (in winter) or an air-conditioner (in summer) and adjust them so that to compensate completely the thermal losses caused by the broken window and to restore the thermal virtual ground.

Hydraulic. Water begins pouring through a hole into the ship's hold because of wreck. In order to keep the desired water level (height virtual ground) the sailors begin continuously pumping out the water instead to plug up the opening. An opposite "hydraulic" example: water begins outflowing from a reservoir because of punching. In order to keep the water level they begin continuously filling the reservoir with water instead to plug up the opening.

Pneumatic. Air flows out the tire since it is punctured. In order to keep the desired air pressure (pressure virtual ground) the driver begins pumping up the tire instead to repair it (in motorized forces, they do that in motion). Another "pneumatic" example: if we pump up a pipe on the one side and pump out it on the other side, a pressure virtual ground appears somewhere along the pipe (we might use an old-fashioned air cleaner, which sucks and blows air through a closed loop made from a corrugated hose for this funny experiment).

Money. I have given another credit card of my account to my wife. Only, she has begun intensely spending my money:((( Trying to keep the desired money virtual ground, I have begun working hard to earn money (instead just to scold my wife). By the way, don't you think that it is interesting the fact that in life whether they work and spend hard or they work and spend little, the result (money virtual ground) is the same:)

Game. In the popular games of arm wrestling and tug of war, a "position" virtual ground appears in the middle when fighting people push and pull with equal power.

Conclusion. 

If we connect each other two opposite power sources by a conductive medium so that their opposite output quantities are superposed (summed), zero or reference level result (virtual ground) appears somewhere along the medium. 

In this "conflict" point, the efforts of the "fighting" sources are "neutralized". The process is associated with continuous energy wasting from both the sources as a result of a continuous energy flow through the medium.

Real Ground Vs Virtual Ground

Real ground is a point with a steady voltage inside the supply voltage source.
Virtual ground is a circuit point with a steady voltage outside the supply voltage source.


(Courtesy: www.circuit-fantasia.com)