Final answer:
To sketch equipotential and electric field lines, one must consider that equipotential lines are perpendicular to field lines and that the configuration of charges (positive or negative) determines the shape of these lines. The position and magnitude of the charges influence the spacing and curvature of the equipotential lines, indicating the strength and direction of the electric field.
Step-by-step explanation:
To predict the equipotential and field lines for various experimental configurations involving electric charges and electric fields, it is important to consider some fundamental principles. Equipotential lines are always perpendicular to electric field lines, and in the case of point charges, they form closed loops around the charges. The position of electrodes, i.e., the positive and negative charges, significantly affect the shape of these lines.
For two opposite charges with one being three times more negative than the other, the equipotential lines would bulge towards the negative charge, reflecting its stronger influence on the electric field. The lines would be closer together near the negative charge, indicating a stronger field there. When illustrating equipotential lines near two conducting plates with opposite charges, the lines would be essentially parallel and equidistant in the region between the plates, especially when the plates are close enough to approximate a uniform field. This uniformity implies that the electric field is strongest where the plates are closest due to the higher gradient of potential in that region.
In the specific case of two equal positive charges, the equipotential lines would be pushed away from the region directly between the charges, forming an hourglass shape due to the repulsion of like charges. For each configuration, the direction of the electric field lines is always from the positive to the negative electrode.