Wed March 26, 2014 By: Gayathri Rajeev

We say that current is not a vector, even though it has direction because its direction is fixed. In the case of dipole moment, its direction is always from the negative end of dipole to the positive end. Then why cant we apply the same convention to a dipole? Why is the dipole moment still treated as a vector?

Expert Reply
Sat March 29, 2014
Electric current I = q/t. As both charge and time are scalars, therefore electric current is a scalar quantity.
Electric curent scalar wuantity
We show electric current in a wire by an arrow to indicate the direction of flow of positive charge. But such arrows are not vectors because they do not obey the laws of vector algebra. This point can be explained y referring to fig. The wire OA and OB carry currents of 3A and 4A respectively. The total current in the wire CO is 3 + 4 = 7A irrespective of the angle between the wires OA and OB. This is not surprising because the charge is conserved so that magnitudes of current in wires OA and OB must add to give the magnitude of current in wire CO.

Dipole moment is a vector quantity as it as a particular direction. Its direction is from negative charge to positive charge along the axis of the di-pole.
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