Magnetic Field In A Wire: 9 Important Facts


Magnetic field in a wire is basically the movement of charges in a given unit area per unit time. When we pass current in a wire there will instantly be both electric and magnetic fields.

Now let us see what actually the magnetic field in a wire means. Now when the current is passed the charges produce the magnetic field in that particular wire and so like this we know that magnetic field is produced.

The moving charges in a wire conduct electricity and also it will create a magnetic and electric field simultaneously. So magnetic field is produced in this way and the current in a long wire is an example of how it is been created.

The strength and magnitude of the magnetic field will decide how much of the flux is been passed through a given unit area per unit time. We must also know that since magnetic field comes under the category of vector quantity it by default will have the magnitude which is the strength and the direction for one particular element.

Is there a magnetic field in a wire?

Yes, there exists magnetic field in a wire. And the reason is the passage of current in the wire. In order to magnetic field to exist in a wire, the wire must be conductor electricity or otherwise there is no point in the magnetic field in a wire.

Considering the wire to be a conductor some amount of current is been passed to the wire, the wire now conducts electricity. Now the charges which are moving inside the wire will produce the magnetic field to exist in it.

The produced magnetic field will now have so many of them called the magnetic flux and will pass through the area. The strength, magnitude and the direction of the magnetic field will decide the amount of flux being passed through the wire.

What is the magnetic field in a wire?

Magnetic field in a wire nothing but the magnetic lines of force passing in the wire when current is passed. The current in a wire is due to the production of charges, the same charges are responsible for the production of magnetic field too.

The magnetic field is simply the charges which have acquired the force of magnetism in and around any material.

When we consider the magnetic field in a wire generally the magnetic field is very strong in the area that is closest to the wire the strength of the magnetic field increases when it is closest to the wire.

Also we need to know that the direction of the magnetic field directly depend on the current which is inducted in the wire.

How to find the magnetic field of a wire?

Consider a straight long wire which is capable of conducting current in them. When the current is passed there will be charges present in them so these charges are responsible for the production of the magnetic fields.

Now we need to find magnetic field in a wire. There will be length for a wire and the height of it too. Also now we need to calculate the magnetic field in a wire using a formula given for it.

Now, since we now that there is a wire conducting wire, there will be length included and since the wire is cylindrical we consider the formula for it too. So then we find the magnetic field in a wire like this, B= µ0 x I / (2 π d).

Here, μ θ= permeability of free space, I= current passing through the wire, d= distance from the wire, B = is the magnetic field produced by the wire.

“Magnetic field” Image Credits: Wikimedia

What happens to a wire in a magnetic field?

When current is passed in a wire there will magnetic field produced by the moving charges due to the electric current, these charges are known to be electrons. The electrons are the reason why there is power given to all electrical materials.

There is something we need to know before we get into what happens to a wire in a magnetic field. Right hand thumb rule is a rule which explains the direction of the current which will influence the direction of the magnetic field.

When the direction of the current is changed it eventually changes the direction of the magnetic field, meaning the direction of magnetic field depends on the direction of current. Electrons are the reason for the conduction of electric current and in turn produces magnetic field too.

The wire will experience a strong force including the electric and the magnetic fields. So when the direction of the magnetic changes the direction of the current has a direct influence to it.

magnetic field in a wire
“Magnetic Field in magnets” Image Credits: Wikimedia

Is magnetic field zero inside a wire?

For a magnetic field in a wire to be zero the internal magnetic field must be a fixed one. When an external magnetic field is applied to the current carrying conductor that is a wire, the internal quantities must be fixed value.

It is been noted that the magnetic field in a wire is zero only for the ideal conductors, that is when the internal factors seem to be a constant. External magnetic field is applied to an ideal conductor, meaning, when the internal magnetic field being always a constant, the magnetic field is generally zero.

When the internal magnetic field is in right angles to the current density and the surface which is normal then the magnetic field in a wire is said to be zero.

There are also other factors which are responsible for the magnetic field in a wire to be zero. When the current induced in a wire is zero the magnetic field will also be zero. Since the magnetic field is produced due to the movement of charges in a wire the magnetic field eventually becomes zero in the complete absence of current.

How can a straight wire produce a magnetic field?

The straight wire must be a conductor in the first place in order to conduct electricity. Next when the current is passed through the wire the charges present in them will produce electric field which in turn will produce the magnetic field.

The charges in the straight wire will move from one end to the other in order producing electric current, also these charges are the sole reason for the presence of magnetic field in a wire.

The charges are positive and negative, the negatively charged ions are named as the electrons which will produce electric current and this in turn produces the electric followed by the magnetic field.

The wire is responsible for the production of magnetic field since it s a conductor. Therefore the straight wire is simply the current producing element that produces the electric and magnetic fields.

“Magnetic field in a wire” Image Credits: Wikimedia

What is the magnetic field for coil?

Magnetic field for coils is simple the current flow in circular loops. When coils are considered the current flow is generally in circular form. Here the current and the magnetic field overlap.

The current is passed in the coil this in turn produces magnetic field and this magnetic field is uniform and also a strong one. So when this magnetic field grows stronger the coil will have a stronger magnetic field and is called as a solenoid.

The coil turns into a solenoid when the current is passed through the coil and in turn producing a strong magnetic field. The solenoid is a coil conducting electric current which converts electrical energy into mechanical energy.

Problem:

 A straight wire is taken and 5A of current is passed through it. Magnetic lines of force is present in the wire along with the electric force. Calculate the amount of magnetic field produced in the wire have distance 2m.

Solution:

B= µ0 x I / (2 π d).

B= 4×107 x 5 / (2×3.14×2)

B= 0.3184 x 107 T

Conclusion

Magnetic field in a wire is found to be the magnetic lines of forces which are acting upon the wire. It us the quantity which is produced when the current is induced in the wire and they also can be zero when the current in the wire is absent. The magnetic field in a straight wire is simply the occurrence when the charges move from one end to another. On the whole magnetic field in the wire is simply the magnetic forces present in the wire when electric current is been passed to the wire.

Keerthana Srikumar

I am Keerthana Srikumar, a post-graduate in Physics. I’m currently pursuing PhD in the area of thin films. I always have a passion for writing and to inspire as many willing minds through my words. Physics is a subject that is used by everyone as basics to navigate their lives. I use writing as a tool to explain it in the most understandable and simplest and way possible. You can connect me through: Email: keerthana48@gmail.com

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