HSC Physics Electric Field Lines

Electric field patterns are commonly drawn incorrectly. A tutorial sheet of field line questions is given below.

  1. Equal point charges +Q and +Q are placed a distance 2d apart in a vacuum. Draw the electric field pattern around these charges. Do the electric field lines approach the perpendicular bisector to the line joining the charges? [see the cover of W J Duffin Electricity and Magnetism]
  2. Point charges +4Q and -Q are placed a distance d apart in a vacuum. Draw the electric field lines around these charges.
  3. Draw the electric field lines of an electric dipole when it is seen close up.
  4. Draw the electric field lines of an electric dipole when it is measured from a large distance (a distance much greater than the charge separation). Is it zero?
  5. Point charges -Q, +2Q and -Q are placed in a straight line in a vacuum. The end charges are each a distance d from the middle charge. Draw the electric field lines around this combination.
  6. A long metal cylinder of inner and outer radii a and b respectively carries a total charge Q. Draw the electric field lines of this arrangement.
  7. A long metal cylinder of inner and outer radii a and b respectively is uncharged. The cylinder is placed in a uniform electric field that is perpendicular to the axis of the cylinder. Draw the electric field lines of this combination.