Why earth ground connection does not leak current?

Question

This seems like a question which has been asked multiple times on forums. I researched the problem but I still was unable to figure out the answer which I can at least intuitively understand. So in this simple circuit why is there no current leakage to earth? Assume that it is a true earth ground connection (a rod in the earth for example).

Update: I am giving researched answers below, but not as the only options. I am not satisfied with any of them, and give my explanation as to why. So I am hoping for either an elaboration or an alternative answer.

^{simulate this circuit – Schematic created using CircuitLab}

The answers I have found:-

1. Here With only one connection to ground there is no circuit for the current to flow through. It can't flow "to" ground, because there is nowhere for it to flow to. There's no difference between ground and a wire dangling in the breeze. However for current to flow there must be potential difference. And because the ground and the battery return has the same potential - why would current prefer to flow specifically to the return point. Especially taken into account that earth can absorb all electrons generated by the battery (on contrary for example to just piece of wire).

2. Here The ground isn't a great conductor and while it is in parallel with the service, the amount of current returning through the ground is so small it is effectively zero - Firstly this answer implies that there's some leakage occurs which just depends on earth resistance. Also I do not understand which resistance is taken into account. Where it is measured? I think also the answer relates to the several connection of the circuit to the ground.

So anyone can give real physical explanation of this?

Answer 1

In reality there is current in the ground connection, but not enough to measure above ambient noise level.

Below is your equivalent circuit.

^{simulate this circuit – Schematic created using CircuitLab}

ADDITION

As such we normally ignore that leakage current in DC circuits. So let us look at your question another way.

For the moment consider what would happen if an electron fell down that "drain" to ground. What happens to the rest of the circuit?

Suddenly it will have a missing electron and will have a net positive charge. The ground now has an extra electron and has net negative charge. That means there is a reverse voltage on the ground wire which will immediately cause the electron to return to the circuit.

The opposite would happen if somehow an extra electron were to arrive from the ground. The circuit would be at a negative potential and ground would be positive. The visiting electron would be immediately repelled.

In actuality, that returning force is what prevents the electrons from crossing the connection in the first place. It is a self stabilizing state.

Answer 2

This is explained by Kirchhoff. He has two laws: the voltage law and the current law.

I won't explain the voltage law, as that is not what your question is asking, but the current law simply states:

The sum of all currents into a node is zero

alternatively:

The sum of all currents out of a node is zero

What this means in the case of your simple circuit is that the current \$I_1\$ flowing out of the top of your battery is equal to to the current \$I_2\$ flowing into the battery.

Since the battery and resistor are in series with the resistor, then the current flowing into the bottom node via the resistor is \$I_1\$.

Let's call the current flowing to earth \$I_3\$.

\$I_3 = I_1 - I_2 = 0 \$ since \$I_1\$ = \$I_2\$.

Answer 3

In the circuit from your question, the earth ground connection function is of a reference point, i.e. a zero potential point. From this point, you can specify all voltages in circuit nodes. It's a convenience for the analysis, say, nodal method.

There isn't relation with current. Is a convention to assign a node as a zero-potential node.

Answer 4

So in this simple circuit why is there no current leakage to earth? Assume that it is a true earth ground connection (a rod in the earth for example).

The circuit diagram shows no elements that would cause a current to flow to ground. If current DOES flow to the 'earth ground' node, is it positive? Negative? AC? DC?

Simply put, this circuit doesn't create any current output, unless other circuit elements exist, which are not shown. If there's a storm cloud, and lightning strikes, there WILL be current to ground. That, however, isn't part of the schematic, so isn't part of the equation. Thus, we're left with 'zero' current predicted.