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  1. What's the point of having the ground near the negative terminal when the electrons would just then flow out of the circuit into the ground?

  2. Since there is already a potential difference between the positive and negative terminals, what's the point of a ground at all?

For example:

enter image description here

Why would ground be on the right? That means in technical current direction, the current would go to the ground and not to the negative terminal and there would be no potential between the ground and the negative terminal...

mikanim
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    https://electronics.stackexchange.com/questions/392010/how-to-find-voltage-based-on-reference-nodes/392063#392063 or this http://www.ittc.ku.edu/~jstiles/312/handouts/312_Introduction_package.pdf (start at page 3 "Electronics circuit notation") – G36 May 17 '19 at 19:36
  • The ground is just a reference point. We just pick a point on the circuit and call it the ground. We can then reference the voltage at every point in the circuit with respect to this point reference point. We have a very similar situation when we try to measure the height of an object. We need a reference point. The most common reference point is "above mean sea level". But when you measure the height of the table in your house the floor now becomes your reference point. And this reference point does not have any influence on the current flow. – G36 May 17 '19 at 19:56
  • As your schematic indicates gnd is just a 0V reference and since it is floating there is no current. – Tony Stewart EE75 May 17 '19 at 20:25

5 Answers5

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In most circuits the ground symbol simply indicates the point in the circuit that we will consider as "Zero Volts", and will use as a reference when measuring voltages elsewhere in the circuit - it is where we place out black meter lead when measuring voltages.

The ground symbol does not necessarily indicate a physical connection to the earth - and even if it did, that connection would not "suck all the electrons away".

Peter Bennett
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  • Thanks for the clarification. To your last point, why not? – mikanim May 17 '19 at 19:51
  • And another question I have now, if electrons are not being "sucked away" to a true earth ground, what is making electrons go to an earth ground from, say, a house? Especially when the earth is assumed neutral. – mikanim May 17 '19 at 19:55
  • @mikanim: See if https://electronics.stackexchange.com/questions/355695/actual-electric-potential-at-terminals-of-battery/355706#355706 helps. Also https://electronics.stackexchange.com/questions/202750/positive-vs-negative-power-vs-ground-flow-direction/208061#208061. Stop thinking of electrons. Just think of current flowing from positive to negative. – Transistor May 17 '19 at 21:01
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Ground defines where 0 volts is. So you cannot place it at the 'negative' terminal, otherwise it would be 0 volts.

For example, if you place 0 V near the '+' side of a 9 V battery, that side will be 0 V, and the '-'side of the battery will be -9 volts. If you place the ground near the '-' side (normal way), than the '+' side is +9 volts and the '-' side is 0 volts.

If you place two resistors in between the '+' and '-' side and place ground between the two resistors, than (assuming the resistors have the same value), the '+' side will be +4.5 volts, the ground in between the resistors 0 volts and the '-'side will be -4.5 volts.

schematic

simulate this circuit – Schematic created using CircuitLab

Michel Keijzers
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  • Right but what about my example? Ground near the negative terminal would make the current go through the ground and not to the negative terminal. – mikanim May 17 '19 at 19:40
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    @mikanim What you just wrote is ***exactly*** what you need to remove from your head. It's flat wrong in every possible way. You are imagining something entirely wrong about "ground" and about "electrons." You need to kill those thoughts, permanently. And replace them with better models (which would be almost ANY model.) You have some very wrong ideas about the universe. – jonk May 17 '19 at 19:43
  • The universe is def an overkill. But I came here to find out the solution hence asking a question on a website that is specifically made to clarify things... – mikanim May 17 '19 at 19:48
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    @Michel, your ground symbols should point to the ground! Not sideways or up. – Transistor May 17 '19 at 20:57
  • @Transistor ... thanks for the comment, I didn't know that ... I thought, if ICs, resistors, and all other elements can be rotated, why not a ground symbol (and it's possible in the schematic editor). – Michel Keijzers May 17 '19 at 21:42
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    Ah! Much nicer. The original earth symbol represents the parallel plates that were buried in the soil to ensure good conductivity. The ground symbol, I think, is similar orientation. See my [Ground, earth and chassis explained](http://lednique.com/tag/ground/). Some schematics use your 'ground' symbol pointing up to indicate positive power connection. Thanks. – Transistor May 17 '19 at 22:01
  • @Transistor Thanks for the explanation and letting me learn something (again). – Michel Keijzers May 17 '19 at 22:26
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What's the point of having the ground near the negative terminal when the electrons would just then flow out of the circuit into the ground?

No, if you measured the current with a meter on ground, you would find that there is no current flowing from this circuit to earth. Why? because all currents must flow back to the battery. A current needs a loop and current flows back to the source.

Since there is already a potential difference between the positive and negative terminals, what's the point of a ground at all?

In this case, for reference. If this circuit was detached from ground, you wouldn't know what the voltages were with respect to ground. It enables you to call 0V the same as earth ground. This can be nice if you have other devices that are connected to ground. If this circuit is in the air, the whole circuit could be floating to different voltages (but they would be the same with respect to each other. In calculations, you need a ground, if there is a system of equations, you need a zero point or it becomes difficult to solve the system of equations.

Why would ground be on the right?

It doesn't need to be, you could put it anywhere in the circuit, the voltages would be different (relative one to another) but the currents and powers would all be the same.

It would be a great exercise for you to solve this circuit by putting the ground at different points and solving for all voltages and currents.

Voltage Spike
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You have heard from somewhere that grounding sucks the electricity. I have heard it too and even said it. It's true for static charge. If I happen to collect it for ex. by walking on a plastic floor and later touch a waterpipe or other to ground connected non-insulating object, a spark jumps from my hand. That's because the earth has a huge capacitance against the infinity, it can easily sink the small amount of free charge that I happen to carry.

The free charge I carry tries to diverge because the charged particles push each other away. Its counterpart somewhere on the floor surely leaks off at least when the floor is washed. Insulator materials such as plastics can catch or inject electrons when their surfaces are rubbed. That's the static electricity. The rubbing generates a thin transition zone between two materials where some free new molecular orbitals exist for electrons and those which have enough energy to float freely, can occupy the available new states.

A battery and a circuit is different. There's no charge unbalance, nothing tries to jump out of the circuit - if some electrons happen to escape (for ex. due thermal vibrations), its positive counterpart which is still in the circuit generates finally so much pull that no more electrons will escape. Thus, if you connect one point of the circuit to the earth, it will not suck the electrons off because none tries to escape.

Term ground in circuits generally doesn't mean earth. It's only a name, a point which is the reference point for the voltages of all other points in the circuit. All voltages are between two points, but for convenience and making designs radically easier, we generally have one point named GND. Then we can easily write "this point XXX has voltage YYY volts". Physically YYY volts is still between XXX and the agreed GND and a voltmeter to see it must be connected between XXX and GND.

  • Thanks for the write up. If electrons are not being "sucked away" to a true earth ground, what is making electrons go to an earth ground from, say, a house? Especially when the earth is assumed neutral. – mikanim May 17 '19 at 20:23
  • When a charged object and non-charged object (=earth) are connected, the interparticle pushing(=electric field) in the charged object pushes the electrons to the initially non-charged object. The balance is achieved sooner or later. Earth is quite big, so quite big amount of charge can get sucked nearly 100,0%. Earth also loses electrons. The wind can catch them like any rubbing which generates static electricity. I bet you have heard of thunderstorms, which are generated by winds. –  May 17 '19 at 20:35
  • @mikanim (continued) in the past and in many modern installations, too, the earth is used as another wire in a circuit. The voltage sources in those circuits push electrons through the earth. –  May 17 '19 at 20:41
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Just to address one of your misconceptions in the comments:

If electrons are not being "sucked away" to a true earth ground, what is making electrons go to an earth ground from, say, a house? Especially when the earth is assumed neutral.

  • Stop thinking of "electrons". Think of current.
  • Current flows in closed loops.
  • If the loop is open circuit no current flows.
  • There is only one earth connection on your circuit so there is no return path out through that connection and back to your circuit. Therefore no current will flow.

Electrons don't get "sucked away". Why do you think they would?

Current only flows in a house earth wire in the event of a fault.

Further reading:

enter image description here

Figure 1 from my answer to How does ground mains work?.

Transistor
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  • I appreciate your efforts but after reading through those answers, I am yet to be satisfied with an explanation. I have searched far and wide for an explanation but I am pretty upset that this stuff isn't explained in-depth SOMEWHERE. This stuff is not self-explanatory and it really does cause unnecessary confusion. Why can't electrical engineers just clarify this stuff once and for all? Even beginner textbooks don't have answers to this stuff...really frustrating. – mikanim May 18 '19 at 20:07
  • Where is the problem? Where did you get the idea that "electrons would be sucked away"? Why, if that was the case, would the earth not *supply* a load of electrons? What would cause them to flow? They will only flow if there is an electromotive force - voltage. – Transistor May 18 '19 at 20:41
  • My current question is more on the lines of: if we earth part of the circuit near the negative terminal, how would that consist of a closed circuit? The current could either go through the ground or to the negative terminal. Would you be interested in discussing anonymously on discord? They have a audio chat function. I'd definitely appreciate it if so. – mikanim May 19 '19 at 10:20
  • After a couple more hours of reading and watching content, I found this video to be helpful: https://www.youtube.com/watch?v=KXjSSvIrKUw – mikanim May 19 '19 at 11:39
  • And this: https://www.youtube.com/watch?v=-n8CiU_6KqE – mikanim May 19 '19 at 11:47
  • And lastly that really helped: https://www.youtube.com/watch?v=zLW_7TPf310 – mikanim May 19 '19 at 12:10