# Magnetic Field due to straight conductor

When a straight conductor carries a current, it creates a magnetic field right along its length. The lines of force are within the style of concentric circles within the planes right angles to the conductor. This will be incontestable by a little experiment.

Think through a straight conductor carrying a current, transitory through a sheet of cardboard as shown within the Fig. Sprinkle iron fillings on the cardboard. Small tapping on the cardboard reasons the iron filling to line themselves, within the homocentric circular pattern. The direction of the magnetic flux may be determined by putting compass needle close to the conductor. This direction is determined by the direction of current passing through the conductor. For the current direction shown within the Fig. i.e. from high to bottom the direction of flux is clockwise round the conductor.

Usually such current carrying conductor is delineated by little circle. Then current through such conductor can either set out of paper or can enter the plane of the paper.
• The cross indicates rear of feathered finish of an arrow.
• The dot indicates front read i.e. tip of an arrow. Current can be conjointly shown in fig.

### Rules to work out Direction of Flux around Conductor

#### Right Hand Thumb Rule:

It states that, hold this carrying conductor within the right hand such that  the thumb inform within the direction of current and parallel to the conductor, then curled fingers purpose in the direction of the magnetic field or flux around it.

Let us apply this rule to the conductor fleeting through card sheet thought of earlier. This will be explained in the above Fig.

#### Corkscrew Rule:

Imagine a right handed screw to be on the conductor carrying current with its axis similar to the conductor and tip inform within the direction of this flow.

Then the direction of the field is given by the direction during which the screw should be turned therefore on advance within the direction of this.