# Magnetic field due to a current carrying conductor is___?

• peeyush_ali
In summary, there is a definite current in an infinitely long wire, even if only positive charges flow.

#### peeyush_ali

In an infinitely long current carrying wire (assuming zero resistance) say there is a definite current.
"Having current in it" means there is a flow of charge in it, which means if positive charge moves in one direction then negative charge moves in opposite direction. As we know that a charge in motion will have to produce a magnetic field which is precisely given by the famous "Biot-Savart 's Law" for a current carrying wire. But is it not this for a normal current carrying wire, that the magnetic field produced by positive charges is equal to that produced by negative charges.
So, when we derive the expression for magnetic field due to an infinitely long current carrying wire the magnitude is given by |B|=Uoi/2 (pi)d where d--->perpendicular distance of the point from the wire and i--->current in the wire.
And that's the expression derived without considering the fact that "in a current carrying wire both positive and negative charges flow" but "only positive charges flow"..there are many textbooks which say exactly the same.
So is this not a violation of obtaining result for something which is not the proclaimed one??
.............
warning..
the probability of this poster to contain irony is finite and maybe nearly one..(or even not)

I don't really get your question, could you rephrase it a little?

One can get the magnetic field due to an infinitely long wire by applying Ampere's law, or Biot-Savart's law. The charges which flow in current are negative charges of the electrons. The positive nuclei of the atoms themselves don't move. The current is defined to move the opposite way as the electrons, but that is just a convention we use. We could redefine convention and change the current to the other direction, but we'd have to redraw every schematic, and redo all the positive/negative signs on all those equations. This turns out to be too big of a hassle.

It doesn't matter what the charge makeup of the current actually is. We can model the current as a flow of ions, electrons, or a mix of the two but the end result is still the same.

peeyush_ali said:
without considering the fact that "in a current carrying wire both positive and negative charges flow" but "only positive charges flow"..there are many textbooks which say exactly the same.
So is this not a violation of obtaining result for something which is not the proclaimed one??

I don't think that I fully understand what you are asking.

But, as has been posted above, I don't think that positive charges flow in a wire.

In semiconductors, positively-charged "holes" (vacancy in the valence band) can flow in electric fields. See

http://en.wikipedia.org/wiki/Semiconductor

The total sum current (electrons plus holes plus ions etc.) is continuous everywhere. It doesn't matter what the makeup of the current is.

Bob S

So, the flaw is there in my question..actually i thought that both positive charges(atomic nuclie) as well as electrons move in a conductor while there is a current in it..there i was wrong..

## 1. What is a magnetic field?

A magnetic field is a region in space where a magnetic force can be detected. It is created by moving electric charges, such as those found in a current carrying conductor.

## 2. How is a magnetic field created by a current carrying conductor?

When a current flows through a conductor, it creates a circular magnetic field around the conductor. The strength of the magnetic field depends on the strength of the current and the distance from the conductor.

## 3. What is the direction of the magnetic field around a current carrying conductor?

The direction of the magnetic field can be determined using the right hand rule. If you point your thumb in the direction of the current, then the curled fingers will point in the direction of the magnetic field.

## 4. How does the strength of the magnetic field change as the distance from the conductor increases?

The strength of the magnetic field decreases as the distance from the conductor increases. This is because the magnetic field spreads out over a larger area as it moves away from the conductor.

## 5. Can the direction of the magnetic field be changed?

Yes, the direction of the magnetic field can be changed by changing the direction of the current in the conductor. If the current flows in the opposite direction, the direction of the magnetic field will also be reversed.