Question

Explain why electric current is not a vector quantity.

Answer 1

Current is a scalar quantity. For any physical quantity to be a vector, not only it should have direction and magnitude but it should also obey the law of vector addition.
Consider two wires A and B carrying equal currents, X amperes, placed at 90 degrees to each other. Now place another wire C at the junction of wires A and B. If you measure the current passing through wire C, the current will be 2X amperes.
If current was a vector quantity, the current which you measured would have been X$\sqrt{2}$ amperes according to the law of vector addition. But the resultant current is 2X amperes.

As current does not obey the law of vector addition, it is not a vector but a scalar quantity.