How does a current carrying conductor produce a magnetic field? I wish to know the exact reason behind it!!?

Answer 1

The quick answer is that current produces a magnetic field because Maxwell's field equations says it does. Look up Maxwell's field equations if you want that answer. However, I suspect you are looking for something deeper.

The best answer to the question of "why" is that electricity does not create magnetism, nor does magnetism create electricity--they are simply one and the same, but we just happen to experience them in two different ways.

Of course, this is a whimsical answer that doesn't really say anything, and obviates the need for an answer. The truth, of course, is that this question of "why" is one that we do not have the answer to. We know the "how," but physics can only rarely (or never) explain the "why."

One of the more charming explanations we discussed in physics was to consider a current to be a series of moving charges separated by a fixed distance. Once the charges are moving, Einstein's special relativity theory predicts the space between each charge will decrease, and thus the concentration of charge increases. This would change how strong an electric field the charges produce, and magnetism could be simply a misguided attempt to explain this inaccuracy.

While charming, of course, the calculations don't quite work out that why, but is is certainly food for thought for a physics student.

Answer 2

1. A moving electric charge always produces a magnetic field.
2. If the charge is accelerating the field is bigger still.
Current involves moving charge.
3. Also a changing magnetic field can induce a current in a conductor. (used in generators)
4. A current carrying conductor in a preexisting magnetic field will experience a force. (used in motors)

All of the above is quantified nicely in Maxwell's equations. I don't think anyone actually knows why those things are true.

Just like no one knows the why of gravity. The why of the nuclear forces are not known.

Why are there three quarks in an electron? No one really knows.

By the way the magnetic field produced from a permanent magnet is also caused by moving charge. In that case it is the electrons moving as a cloud around the nucleus of each atom. In most materials the magnetic fields cancel out but in a few materials like iron not all the fields cancel and there is a residual magnetic field. If the magnetic domains of the metal line up the same way there is a measurable field that results.

Answer 3

Vell, vonce upon a time, God was working on electricity and when God wanted to the electricity to move, but not make a magnetic field, God found it was static electricity and was only on the surface and didn't move well, so God tied the two together as electro-magnetism and required that every instance of magnetism produce an electrical component and every instance of electric currant produce a magnetic field. And it was good.
Or you could say that both are produced by electrons which have a charge and a field and they interact.

Answer 4

The motion of the electrons creates the field, according to Maxwell's equations. See:

Answer 5

Nobody knows why.

Back when Aristotle was explaining the "nature" of things he was trying to explain WHY things happened.

These days we explain HOW things happen. Sure, you have equations and formulas but nobody explains what electromagnetism REALLY is.

Answer 6

In physics, a magnetic field is an axial vector field that traces out solenoidal lines of force in and around closed electric circuits and bar magnets. These lines of force pull unlike magnetic poles together and hence cause a compass needle to align in the axial direction of the magnetic field. A lateral repulsion between adjacent magnetic lines of force causes like magnet poles to repel each other.

For a closer look at the effects of a magnetic field, see under ferromagnetism, paramagnetism, diamagnetism, electromagnetism, and electromagnetic induction.

The magnetic field is a relativistic consequence of more fundamental electric field.

Definition

The following equation for magnetic field \mathbf{B} is a version of the Biot-Savart law and it is a solution to Ampère's law.

\mathbf{B} = \mathbf{v}\times \frac{1}{c^2}\mathbf{E}

where

\mathbf{v} \ is velocity vector of the electric charge, measured in metres per second
\times \ indicates a vector cross product
c is the speed of light in a vacuum measured in metres per second
\mathbf{E} is the electric field vector measured in newtons per coulomb or volts per metre

As seen from the definition, the unit of magnetic field is newton-second per coulomb-metre (or newton per ampere-metre) and is called the tesla. The magnetic field vector is a pseudovector or axial vector, rather than a simple vector, as it represents an axis. Like the electric field, the magnetic field exerts force on electric charge — but unlike an electric field, it exerts a force only on a moving charge:

\vec{F} = q \vec{v} \times \vec{B}

where

\vec{F} is the force vector produced, measured in newtons
q \ is electric charge that the magnetic field is acting on, measured in coulombs
\vec{v} \, is velocity vector of the electric charge q \, measured in metres per second

Intuitively \mathbf{B} can be seen as a vector whose direction gives the axis of the possible directions of the force on a charged particle due to the magnetic field; the possible directions being at right angles to the axis \mathbf{B}, and the exact direction being at right angles to both the velocity of the particle and \mathbf{B}. The magnitude of \mathbf{B} is the amount of force the magnetic field causes on the particle, per unit of particle charge by particle speed. Another intuitive way to view \mathbf{B} is as a bundle of lines of force that pull two unlike magnetic poles together.

Magnetic field of current flow of charged particles

Substituting into the definition of magnetic field

\mathbf{B} = \mathbf{v}\times \frac{1}{c^2}\mathbf{E}

the proper electric field of point-like charge (see Coulomb's law)

\mathbf{E} = { 1 \over 4 \pi \epsilon_0} {q \over r^2} \hat{r}= {10^{-7}}{c^2} {q \over \ {r}^2} \hat{r}

results in the equation of magnetic field of moving charge, which is usually called the Biot-Savart law:

\mathbf{B} = \mathbf{v}\times \frac{\mu_0}{4 \pi}\frac{q}{r^2}\hat{r}

where

q is electric charge, whose motion creates the magnetic field, measured in coulombs
\mathbf{v} is velocity of the electric charge q that is generating \mathbf{B}, measured in metres per second
\mathbf{B} is the magnetic field (measured in teslas)