The Electric fields

This lecture is based on HRW, Sections 23:8-9

An electric charge q in an electric field E feels a force
```
               F =  q E
  
```
The direction of the force is the same as that of E (if the charge is positive) or opposite to it (if charge is negative).
A charged object in a uniform electric field feels a constant force, and hence undergoes a uniform acceleration -- just like an ordinary object in the uniform gravitational field near the Earth's surface.
An electric dipole p in a uniform electric field E feels a torque which causes it to rotate:
```
            torque =  p x E
  
```
The direction of the torque is given by the vector cross product of p and E.

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