Name: An Elementary Study of Domestic Electric Circuits
Uploaded: 2019-07-19
Duration: 5 min 52 s
Description: The electricity we consume is produced through electromagnetic induction at power plants. In this video, we will see the journey of electricity from the powe...

Question

With the help of a labelled circuit diagram illustrate the pattern of field lines of the magnetic field around a current-carrying straight long conducting wire. How is the right-hand thumb rule useful to find the direction of the magnetic field associated with a current-carrying conductor?

Accepted Answer

Consider the following diagram.

A battery, a variable resistance (or a rheostat), an ammeter, a plug key, connecting wires and a long straight thick copper wire are conected in series. The thick wire through the centre, normal to the plane of a rectangular cardboard. When the circuit is complete, as the current passes through the wire magnetic field is set up around it as shown in the figure. The magnetic field lines observed have the follwing properties:-

The magnetic field lines are in the form of concentric circles near the conductor. However, somewhat away from the conductor, these field lines tend to be elliptical, because of the combined effect of earth's magnetic field and the magnetic field due to the conductor.

The plane of the magnetic field lines is at right-angles to the plane of the conductor carrying current.

The direction of the magnetic field lines reverses with the reversal of the direction of current in the conductor.

On increasing the strength of the current in the conductor, the number of magnetic field lines around it increases. In other words, the intensity of the magnetic field increases with the increase in the strength of the current.

It is observed, that if the experiment is conducted at any point on the conductor, the concentric field lines are formed around it. From this we can conclude that conductor on the whole is surrounded by a cylindrical shell of magnetic field lines.

The direction of the magnetic field set up around the coil be determined by Right hand thumb rule. According to this rule, imagine that you are holding a current-carrying straight conductor in your right hand such that the thumb points towards the direction of current. Then your fingers will wrap around the conductor in the direction of the field lines of the magnetic field.

With the help of a labelled circuit diagram illustrate the pattern of field lines of the magnetic field around a current-carrying straight long conducting wire. How is the right-hand thumb rule useful to find the direction of the magnetic field associated with a current-carrying conductor?

Important Questions on Magnetic Effects of Electric Current

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