How long must a 0.70-mm-diameter aluminum wire be to have a 0.40 a current when connected to the terminals of a 1.5 v flashlight battery?

By using Ohm's law, we can find what should be the resistance of the wire, R:


Then, let's find the cross-sectional area of the wire. Its radius is half the diameter,

So the area is


And by using the resistivity  of the Aluminum, , we can use the relationship between resistance R and resistivity:

to find L, the length of the wire:

Sound energy is produced when an object vibrates. examples are 1- a balloon popping2-a whistle3- a waterfall

One splits the atoms and molecules  the other combines them