Fundamentality of voltage to current From Ohm's Law : 

Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points.



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*I would like to know if writing $V\propto I$ is the same as writing  $I\propto V$?

*Are they both correct?

*Are they equally dependent on each other or is only current dependent on the voltage? 

*Because in  circuits it is the voltage that we have as constant and not the current or is there a way to make the current the factor that determines the voltage?
 A: If you are wondering about causality, then I think that voltage difference $\Delta V$ is fundamental as it is the cause, and the current $I$ is the consequence.
If you want to have current, you need movement of the charges.  The most obvious way to move charges is to act upon them with electric field, and each electric field is accopmained with voltage difference.
I real terms I cannot think of the quasi-electrostatic process - and Ohm's law does describe quasi-electrostatic process - in which the current would create the voltage.  Hence,
$$I \propto \Delta V.$$
An interesting connection to the interpretation above are constant voltage and constant current sources.  Constant current sources are actually voltage sources with quick loopback that changes voltage in order to keep the current constant.
A: Yes, if you write $V \propto I$ it means:
$$V = kI$$
for some constant $k$. If you rearrange this equation to:
$$I = \frac{1}{k}V$$
this is the same as:
$$I = k^'V$$
for a new constant, $k^'$, and therefore $I \propto V$.
Response to comment: in some situations it makes sense to think of the current dependent on the voltage, but in others you would think of the voltage dependent on the current.
For example, suppose you have a battery with a known voltage, $V$, and you want to know the current. You'd normally write:
$$I = \frac{V}{R}$$
and feed in the voltage, $V$. On the other hand suppose you have some resistor, $R$, with a known current, $I$, flowing through it and you want to know the voltage drop accross the resistor. In that case you'd write:
$$V = IR$$
And of course there's a third case where you have a battery with a known voltage, $V$, and you measure the current to be $I$, you might ask what the resistance is. In that case you'd write:
$$R = \frac{V}{I}$$
All three of these equations are just rearrangements of each other, so they're all basically the same equation. You just rearrange them to suit the question you're trying to answer. This is pretty common in Physics. In due course you'll learn about ideal gases where there's a similar equation $PV = RT$, and you rearrange this equation in different ways depending on what you're trying to calculate.
