The cause of electrical resistance(in a metal) is electrons colliding with themselves and the positive ions. So if the electrons collide with the positive ions, how are they able to overcome the attractive force due to the positive ions (in a metal)?
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Electrons and ions are quantum mechanical entities. The model you have in mind is of classical charged particles,whereas it is quantum mechanical models that can reconcile microscopically how current is created.
Metals form lattices. Lattices have the ions in specific symmetric sites and the electrons, depending on the material, are modeled with something like the band theory of solids.
There is the valence band, electrons in the bound energy levels around the nucleus, and the conduction band. Electrons in the conduction band are not bound to an individual nucleus but to the lattice as a whole, and can be considered "free" to move through the lattice , which allows this microscopic view of current. The electrons making up the current are not "colliding" with the ions of the lattice, they are in a bound state of the lattice and do not "see" individual atoms.
