Thank you everybody.
Now I understand the coefficient friction can be higher than 1.
Another explication is that in a ramp, the coefficient of friction is equal to the tangent of ramp's angle.
The angle can be higher than 45º, so the tangent would be also higher than 1, as a consequence...
But if you are talking about glues and something like this, you are not talking about friction, it's a different force.
For definition, when the coefficient of friction is m:
0<=m<=1
And I wonder, why m<=1?
Yes, so the problem is that I=V/0, somebody can explain what happens to the electric current?
It's right that it's impossible to get absolute zero (for the moment). But We can also get zero electric resistance if we use perfect superconductors in low temperatures.