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.