Electronics is very new to me.
I took the most basic circuit I could think of: A voltage source of 1V and resistor of 1 Ohm
As far a I understand I should get a current of (I = V/R) 1 Ampere. But the simulation does not give a solution and said I should have ground.
Why should I have ground if I have a voltage source that gives potential differences from its two sides?
I attach the circuit:
https://www.circuitlab.com/circuit/839aaj6y5a6t/simplest-circuit/
You are absolutely correct: Voltage is only defined between two nodes.
In many electronic circuits there is a constant-voltage* power supply that connects to many parts of the circuit. By convention, the more positive terminal of the power supply is labelled "V+" or "Vcc" or...
By convention, the more negative terminal of the power supply is called "ground."
By convention, we often do not draw either the V+ net or the ground net in circuit diagrams. Instead we connect things to a V+ symbol or, to a ground symbol.
And finally, by convention, whenever we talk about the voltage at any point in the circuit, we are implicitly talking about the voltage between that point and the ground net.
Your simulation tool is simply honoring that last convention. Therefore it requires a reference net called ground.
* or, some approximation thereof
the specifics of the question is:
As far a I understand I should get a curent of (I = V/R) 1 Amper. But the stimulation does not give a solution and sais I should have ground.
Why should I have ground if I have a voltage source that gives potential differences from its two sides?
It comes down to how simulators work. Simulators require a reference point and this reference point is designated by the GND symbol. internally, the engine will determine the system equation and responses against this reference.
This limitation doesn't exist in the real world because of physics.
Normally it is 'assumed' that the minus (-) side of the power supplier is 0V, so if you connect the ground to the minus side, that will be 0 V. and the plus (+) side will be 1V (GND + difference = 0 + 1 = 1)V.
If you would put the ground at the plus side, the minus side would be -1V.
You are quite right. The "output" node can't measure a voltage unless it is told the other point to compare it with. That is the sole purpose of the "ground" point.
If you don't ask for a voltage to be measured, you might think it could at least measure a current at a node. But the SW needs to calculate voltages in order to calculate currents, so it needs a ground reference point for its own calculations.
Why should I have ground if I have a voltage source that gives potential differences from its two sides?
The reason is how you describe the circuit. You're right. all voltage is across 2 points. There is no such thing as "what's the voltage at point IN", you can only tell "what's the voltage between IN and OUT".
Therefore, to simplify talking (and thinking) about a circuit, it's common practice to declare something in the circuit as "this is zero" and call it "ground". So you can say "Voltage at IN is 1V", but what you actually mean is "Voltage between ground and IN is 1V".
It's expected that a simulator won't work without ground by just looking at it. It shows voltages "at points", not "between points". Without setting the ground point, it's not possible to present results this way, so it's pointless to run the simulation at all.
I suspect that there are some simulators that would work. It's not a technical problem, it's the problem of how results are presented.
Actually, you don’t need a “ground”. What you need is a connection between the bottom of the resistor and the bottom (negative) terminal of the voltage source. In a simulator this is done by a connection list. If these two are connected to a water pipe, the top of a Tesla coil, the 220 volt AC power, the top of a Van De Graf generator, or Ben Franklin’s kite, the current in the resistor calculated by the simulator will be the same.
So go back to your simulator and make sure there are connections to TWO DIFFERENT points on the voltage source and to two different points on the resistor.
Remember: resistance is futile!
I will try to answer your question in a strictly math sense.. You will understand why the poor chap called the simulator is unable to find a solution here.
Your Circuit is as follows
Lets call the upper terminal A and the lower one B as shown in figure.
Now we know for your voltage source \$ V_A - V_B = 1V \$
We also know from the resistor side that
\$ I = (V_A - V_B) / R \$ which is \$ I= 1 \$
Now I can give you infinite number of \$ V_A \$ and \$ V_B \$ which still satisfy \$ V_A - V_B = 1 \$
For example \$ V_A=5 \$ & \$ V_B=4 \$ still gives \$ V_A-V_B=1\$ and this is a valid solution.
Can you see why the simulator cannot solve it ? Bcz there is no unique solution to \$ V_A \$ or \$ V_B \$ here.
All the voltage differences and currents are still defined.. But absolute voltages are not..
For absolute voltage to be defined ( and for ur simulator to throw a solution ). You need a reference. That reference is usually chosen as ground.
When you define either \$ V_A \$ or \$ V_B \$ then a unique solution exists.
General practice being.. make \$ V_B=0\$
We see that then the Solution for \$ V_A=1 \$ You Can force \$ V_B \$ to any other voltage.
Think of a even simpler situation:
Lets say that there is 20 storied building ( lets say that each floor is 10ft in height). and lets say you are standing on the 12th floor of the building.
If someone asks you at what height you are standing..
What would your answer be ?
120ft ? Are you sure ?
What if the building is on Mt.Everest ( which itself is some 29000ft from sea level ) ?
Although you can say that from the 0th floor to you.. the difference is 120ft.
Although you can say that from the 1st floor to you.. the difference is 110ft.
You cant define your absolute height unless you know from where you are measuring.
If you are building is on Mt.Everest and your reference is Sea level. then the height at which you are standing is 29000ft + 120ft.
If however your reference is the 0th floor, the height is 120ft.
I hope you understand the difficulty the simulator is facing.
Simulate the below two Circuits and you will understand what I am speaking of..
Zeroth floor being the reference :
Sea level being the reference :
All the best !!
For a simple circuit, you are right. Your diagram can run without a ground.
Actually, when you connect those elements in real word you can measure current and voltage whereever you want so it is legit.
The simulator is software and it is designed to calculate all possible circuits, so in some curcits you need a ground to understand the circuit.
Considering your circuit I can show you en example
Either anode or catode can be grounded right?
Lets assume we put the positive pin of the power source to the ground.
The circuit will work fine but there is no point you can measure a positive voltage on the circuit, but the physical reality won't change. (That is, the current or heat production or power consumption etc.)
If the negative pin is grounded then we can measure positive voltage, but everything else remain the same Power consumption, heat, current and its direction, etc.
As you said it is relativ which means they are same. If you say I am 5 cm taller than my friend or if you say my friend is 5cm shorter than me.
The software asks you which one do you want me to say.
Ground is the reference point. Where you put the ground will change the sentence and not the results.
Please ask any further questions if you need any more clerifacations.
The physics of the circuit does not require a ground. The measurement of the voltage on a real circuit between two points does not require a ground.
The simulator program has a simplified interface where one node is always considered the reference node, aka Ground. It could have been written more generally, but the first way was easier, so you are stuck with it.
As most applications do use a ground, and most people do want to think of voltages with respect to a '0' point, there has never been any call for the more complicated interface that would involve specifying your reference node for every voltage measurement. Most simulators have a dedicated 'differential voltage probe' for when you want to do that anyway.
Actually there are two reasons.
First It is a simulation. In the real world if you connect a 1 V power source (with a high current capacity(which means a powerfull voltage source not a common AA type battery)) to an 1 Ohm resistor you will definitely get 1 A without any grounding.
But..
Secondly it is also used on real world to create negative voltages. And the simulateor wants to know which one you are trying to do. If you ground the negative side of the power source the circuit is the equalient as you did not ground it (almost equalient) But if you ground the positive side of the power source although the function of the circuit does not change the measurements on the circuit will and that would make a difference .
In the first example when you ground the bottom part (- end) youU ve 1 V and 0 volt (ground) , difference is 1 V and current is 1 A. But On the second example when you ground top (+ end) you will have -1 V on bottom and 0 volt on top , the difference is 1 V and the current is 1 Amper. The both circuits function exactly in the same way but the measurements are +1 to 0 versus 0 to -1. And they are different in that way. SO the simulator asks you for a decicion about which one you want to bulid.
