Beginners idiot question

[magic]

Only if it's a superconductor.

OP is asking about simulation, not real cables.

Simulators always assume the resistance between ground connections is lower than the wires, which also confusingly have zero resistance. [...] SPICE considers the ground nodes first, so if they're connected together with other wires, then the current in those wires is assumed to be zero.

Maybe that's what SPICE does but OP sees exactly the opposite behavior.
It's irrelevant either way, it's just a simulation of "ideal" components which don't exist so it doesn't need to make sense.

[ArthurDent]

Mr D

Ok, so am i right in thinking that in these circuits / discussions, the word "ground" could be replaced with "the negative terminal of the battery"?

The replies to this topic are starting to make the question far too complicated. This is like when a young child asks: “where do babies come from?” and the parent goes into a very long and uneasy sex-ed explanation when all the child wants is: “the hospital”.

There are lots of circuits that have absolutely no ground, or earth, or whatever you want to call it. An automobile is isolated from ground by the tires, an airplane in the air has no ground connection, and a space station has no connection to ground when in orbit. To check or troubleshoot the circuitry in each of these examples you have to choose a somewhat arbitrary point of reference if you are going to describe the voltages at various points in the circuit to others.

If someone asks: “what is the voltage at B?” you have to ask: “with respect to what?” When you ask. above, whether to use “ground” or “the negative terminal of the battery”, both are not the answer, it is "the reference point specified". Check the link below for a better explanation.

http://www.tpub.com/neets/book1/chapter3/1-18.htm

[Macbeth]

OP should just breadboard (who even needs a breadboard for such a simple circuit?) and use the cheapest crappiest DT830 or other meter possible and figure it out for himself. 

[Brumby]

 

The Op has not expressed any difficulty with circuit operation - just the way it is being represented by the simulator he is using.  His comment about current sharing through the common wire and the ground connections demonstrates he has a reasonable grasp of what to expect in a real circuit - it's just that the simulator isn't showing that:

.... But what i don't understand is why EC shows the current only flowing through the bottom horizontal wire.
If the grounds are connected (as proved by the circuit on the left), then the current should flow just as happily through this ground bus, right?!
So i'd expect, all other things being equal, that we'd have 50% of the current flowing through the bottom horizontal wire, and 50% through this real or virtual ground bus!?

[Brumby]

For the benefit of the Op, maybe it's time to roll this out again.....

[vk6zgo]

It's just one of the idiot things simulators do!
Another one is that as a default, LTspice shows an ac source as a DC one, then has a note alongside saying what it really is.

LTSpice shows a voltage source as a voltage source.  You then define what kind of voltage waveform you want it to provide.

An ac voltage source is not, in normal schematics shown with + & - signs----- a DC voltage source is.
The very presence or non-presence of the polarity signs defines which it is.

Having the default a DC source is misleading.
Standby for multiple "Noobs" becoming confused & drawing real schematics this (incorrect) way.

I tried to like LTspice---- I really did!, but when it I couldn't simulate a basic CR network, I gave up.

This is a PEBCAK problem, not LTSpice.

It's a bit like trying to remove cylinder head bolts with a Stilson Wrench------it might work, but it will take 10 times as long, & a lot of scraped knuckles along the way!

It's like trying to use a tool you haven't yet learned to use.

When I learnt Electronics, the designers of LT spice were but a sparkle in their Father's eyes.

We had a number of ways to determine the operation & performance of circuits.

(1) Use our imagination & our knowledge of theory to visualise how it would work.
(2) Work through the mathematics.
(3) Steal someone else's design.
(4) Build the circuit up & test it in the real world.
(5) A combination of the above.

If I have to devote a not inconsiderable part of my limited time on this Earth to learning how to use a particular underwhelming  "tool", I'd rather use one I know how to use.

And, by the way:- "Get off my lawn!" 

[Zero999]

Only if it's a superconductor.

OP is asking about simulation, not real cables.

Simulators always assume the resistance between ground connections is lower than the wires, which also confusingly have zero resistance. [...] SPICE considers the ground nodes first, so if they're connected together with other wires, then the current in those wires is assumed to be zero.

Maybe that's what SPICE does but OP sees exactly the opposite behavior.
It's irrelevant either way, it's just a simulation of "ideal" components which don't exist so it doesn't need to make sense.

You're right.

LTSpice doesn't do that. The simulator the original poster is using must do it the other way round: calculate the current in connections before the grounds.

The simple way to avoid this confusion is to not connect more than one ground symbol to a wire.

[Zero999]

It's just one of the idiot things simulators do!
Another one is that as a default, LTspice shows an ac source as a DC one, then has a note alongside saying what it really is.

LTSpice shows a voltage source as a voltage source.  You then define what kind of voltage waveform you want it to provide.

An ac voltage source is not, in normal schematics shown with + & - signs----- a DC voltage source is.
The very presence or non-presence of the polarity signs defines which it is.

Having the default a DC source is misleading.

Standby for multiple "Noobs" becoming confused & drawing real schematics this (incorrect) way.

All right, I'll bite.

You've missed the point. SPICE doesn't need schematics. They were added later and there is no default voltage source symbol. LTSpice has both AC and DC voltage source symbols. It's easy to choose the correct one and it's not the software developer's fault, if user makes a mistake and clicks on the wrong one. Even if the user has used the wrong symbol, there's a piece of text next to it clearly showing whether it's AC, DC or both (quite often you want a signal with both AC and DC components).

I tried to like LTspice---- I really did!, but when it I couldn't simulate a basic CR network, I gave up.

This is a PEBCAK problem, not LTSpice.

It's a bit like trying to remove cylinder head bolts with a Stilson Wrench------it might work, but it will take 10 times as long, & a lot of scraped knuckles along the way!

It's like trying to use a tool you haven't yet learned to use.

When I learnt Electronics, the designers of LT spice were but a sparkle in their Father's eyes.

We had a number of ways to determine the operation & performance of circuits.

(1) Use our imagination & our knowledge of theory to visualise how it would work.
(2) Work through the mathematics.
(3) Steal someone else's design.
(4) Build the circuit up & test it in the real world.
(5) A combination of the above.

That's all well and good, until you work on a project containing hundreds of transistors, etched into a single piece of silicon. It becomes too costly to get an IC made, just to test a concept, hence the need for a virtual breadboard, allowing the designer to test it first. If it wasn't for SPICE, you wouldn't be able to type that message and post it, because the Internet wouldn't exist.

If I have to devote a not inconsiderable part of my limited time on this Earth to learning how to use a particular underwhelming  "tool", I'd rather use one I know how to use.

And, by the way:- "Get off my lawn!" 

That's fine. No one is making you learn how to use it and by the way, get off the LTSpice threads!

[Brumby]

Could I please suggest that you not continue this tangent "discussion" on this thread.

This is the beginners section and we don't need to bury the Op in stuff that isn't directly helping him.

[vk6zgo]

Could I please suggest that you not continue this tangent "discussion" on this thread.

This is the beginners section and we don't need to bury the Op in stuff that isn't directly helping him.

Why not! ---- That's what we always do!

[AlfBaz]

Just noticed this:

Just noticed this:

Both grounds are at the same potential so with no potential difference there is no current flowing.

Sorry, but that is an absolutely incorrect statement.

Current CAN flow through a conductor without any potential difference across it, when it is part of a circuit that has current flowing because of the other circuit elements.  In fact, this is the definition of a conductor (in the normal sense).

Given the context of the answer ie why something isn't something happening in a simulator and your stance on not confusing the OP, why then do you write a paradoxical statement that can be proven mathematically to be false and then allude to mysterious elements that are not part of the current( ) problem

Ltspice shows zero current if you try to parallel "wires" and spice in general does not simulate connection properties. If you want a wire in your sim you'll have to model it

[Brumby]

Just noticed this:

Just noticed this:

Both grounds are at the same potential so with no potential difference there is no current flowing.

Sorry, but that is an absolutely incorrect statement.

Current CAN flow through a conductor without any potential difference across it, when it is part of a circuit that has current flowing because of the other circuit elements.  In fact, this is the definition of a conductor (in the normal sense).

Given the context of the answer ie why something isn't something happening in a simulator and your stance on not confusing the OP, why then do you write a paradoxical statement that can be proven mathematically to be false and then allude to mysterious elements that are not part of the current( ) problem

Ltspice shows zero current if you try to parallel "wires" and spice in general does not simulate connection properties. If you want a wire in your sim you'll have to model it

Apologies.

My response was based on the real world situation, where I now see you were talking about "why something isn't something happening in a simulator".

Apologies to the Op as well.