Sketch the electric field lines in the vicinity of the conductor in Figure 18.48 given the field was originally uniform and parallel to the object’s long axis. Is the resulting field small near the long side of the object?
Step 1 of 4</p>
Conductors contain free charges that can move freely. When excess charge is placed on the conductor it gets distributed on the surface of conductor uniformly. Moreover when a conductor is placed in a electric field charges get rearranged and the steady state known as electrostatic equilibrium.
Under the effect of electric field free charge move until the field is perpendicular to the surface. No component of field can be parallel to surface because if the parallel component of field is present it will further move the charge till the field on this charge becomes perpendicular.
Further, the charges on the conductor get polarized under the effect of electric field. The free charges move inside the conductor, polarizing it, until the field becomes perpendicular to the surface.
Step 2 of 4</p>
If a conductor has uneven surface or has sharp edges, excess charge gets concentrated on the sharp edges under the effect of electric field due to rearrangement of charges to make electric field perpendicular to the surface. On a flatter surface the parallel component of field is greater which moves the unlike charges away from each other than the curved surface.
Moreover excess charge may move on and off the sharp edges which is main reason of construction of pointed edges lightening rods as shown below.