The physical meaning of imaginary number J

imaginary number $j$ When solving a system of cubic equations in one variable , To give $j$ The square of is equal to $-1$ Introduced by a solution , but $j$ The meaning of
What is it? It's not clear at all .

imaginary number $j$ The physical meaning of ： One The plural And $j$ Multiplication is equivalent to the vector corresponding to this complex number in Complex plane On Counter clockwise rotation $90˚$. After figuring this out ,$j^2=-1$ That's a good explanation , As shown in the figure :

$j^2=1\ast j\ast j$
That is to say $1+0j$ The vector of this complex plane , Rotate counterclockwise twice , That is to say $1\ast j\ast j$, So the result is $-1$

In one sentence ：
The vector of the complex plane rotates counterclockwise $90^o$