Electric field patterns are commonly drawn incorrectly. A tutorial sheet of field line questions is given below.
- 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]
- Point charges +4Q and -Q are placed a distance d apart in a vacuum. Draw the electric field lines around these charges.
- Draw the electric field lines of an electric dipole when it is seen close up.
- 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 the field zero at a large distance?
- 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.
- 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.
- 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. What is the electric field strength inside the cylinder?