Two conductor are parallel and  have same direction of flow of current .what will be the force between them repulsion or attraction. And why ,explain

The current through both the conductors is in the same direction.

 

Hence, using the right-hand thumb rule, the direction of magnetic field will be as shown in the figure below.

 

 

Now, Fleming's left - hand rule gives the direction of force by keeping the index finger in the direction of field, the middle finger in the direction of current and the thumb will point in the direction of force on the conductor.

 

Therefore, on the left conductor:

 

Out: Force is in the right direction

 

In: Force is in the left direction

 

And, on the right conductor:

 

Out: Force is in the right direction

 

In: Force is in the left direction

 

Now, the far points on the conductor do not have large effect. So, the points inside the conductor overpower the points outside.

 

 

Hence, the two conductors will repel each other.