Difference between electrostatic lens and electromagnetic lens Imagine an electron-beam in a scanning electron microscope.
From what I've gathered usually electro static fields are used to accelerate the electrons to a desired speed.
At the same time electro-magnetic lenses are usually used to change the path of the beam i.e. to focus the beam and change directions of the beam.
My questions are:


*

*How does one create an electrostatic field/electrostatic lens? I know that a electromagnetic lens is created by running a current through a coil.

*What forces act on the electrons in an e-static lens that accelerate the electrons? Again I know of the Lorentz force in the electromagnetic case.

*If electrostatic lenses are able to change direction too, why are we using electro-magnetic lenses for this purpose?
I already tried to look this up, but was only able to find the electro-magnetic side of things. 
 A: electrostatic lenses are used in low energies (low speeds), because they are simpler to build. Just get two well-polished metal plates and put a high voltage across them and you get a relatively uniform electric field that can bend electron paths. These take advantage of Coulomb's Law, which scales with the electric field only.
However, as said in previous comments, they don't scale well at high energies (high velocities) because the electrons are spending far less time in the electric field for the force to be acting upon it. So you end up having to make them longer, and strengthen the electric field. When you do this, you make the device much larger and more expensive, and suddenly it's no longer a viable microscope for a modest lab.
Enter electromagnetic lenses. These things use the Lorentz Force, which scales with the electron's velocity. This means that faster moving electrons through a magnetic field cause stronger forces on those electrons. You only need to build a strong enough B field to get the sort of redirection you want, and the same lens can cover a wide range of beam energies.
A: Electrostatic lenses use opposed plates with high potential difference. This creates an electric field which accelerates electrons toward the anode. This is essentially a capacitor so the electric field can be modulated very quickly for steering the beam.
Electromagnetic lenses use inductive coils to create a magnetic field. The force (and therefor acceleration) exerted on the electron is given by the right-hand rule, where force is orthogonal to electron movement and magnetic field vectors. Inductors resist change in magnetic field and so cannot be modulated fast enough to steer the beam. It is, however, uniquely able to modulate the convergence of the electron beam to focus it to a point or small area.
