Grounding confusing. Especially when it comes to electronics. I think that most people who have begun to study electronics at one time or another asked, "What is the earth here in the diagram?". This connection to the earth?
The whole point is that the land in the electronics and high-voltage electrical circuits - are one and the same words, but with a different meaning. In the high-voltage circuits, the term "grounding" means the actual connection to the land.
Typically, in electronics grounding - it's just a "name", we give a certain point along the chain.
The circuit with one battery (with positive and negative terminal), we usually refer to the negative terminal grounded.
Now I will try to explain with examples.
To see how the current flows in the circuit diagram with the symbols of the ground, just connect the points that have ground the characters together.
Circuit where there is a "plus", "minus" and "grounding"
In some schemes, you can find a connection to the terminal "plus" terminal "negative" and the ground terminal. It is common, for example, amplifier circuits. What's the "secret" and "how it works"?
In this embodiment, the land is a midpoint between plus and minus. If the voltage measured between the plus and minus is 9 volts, this means that the ground will be at 4.5 volts. But in this case, the terminal "plus" there is a potential of 4.5 volts, to terminal "a minus" - 4.5 volts. On the ground terminal will therefore potential is 0 volts.
I remind you that the voltage is the difference in potential between two points. Thus, if the terminal "minus" and -4.5 volts at terminal "plus" 4.5 volts, then we have a potential difference (voltage) between 9 volts.
If you're wondering how you can power such a scheme (Fig. 1) - just connect the two power sources, such as: