In a conductor when electrons flow, i.e the current flows there is a magnetic field developed across the conductor. 

The mutual force that exists between two parallel current-carrying conductors will be proportional to the product of the currents in the two conductors and the length of the conductors but inversely proportional to their separation.

In the below equation, i1 and i2 are the currents in the two conductors (in Amperes), L is the parallel length of the conductors (in meters), D is the distance separating the two conductors (in meters), F is the force (in Newton's), and k is a constant.

F= k. i1.i2 L/D

Right Hand rule

With the thumb, index, and middle fingers at right angles to each other (with the index finger pointed straight),

the middle finger points in the direction of c when the thumb represents a and the index finger represents b.

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