In one (Why is heat a scalar quantity?) of the questions I answered, I came across this:-
A vector quantity should obey the law of vector addition.
But I don't think it is true. Consider a y junction circuit containing 3 identical wires. If i current flows through each of the 2 arms, the current through the other wire is 2i. But the current density vector of each arm doesn't add vectorially to give the current density in the third.
I want to know whether vectors should obey the law of vector addition or not.
Thanks in advance.