Note that I mentioned d1>d2, this is incorrect, d1<d2 as per the written version in the video.
Things to note:
· Field pattern should be symmetrical (assume charge on the two spheres are of the same magnitude: check symmetry - up vs down; left vs right)
· Spacing of field lines should be further as they move further from the charges (indicating a weaker field)
· Field lines should emerge perpendicularly from the surface of the charge (assuming that these spheres are sufficiently small and that the charges on the sphere do not redistribute themselves)
· For part c) some students will say that the presence of the two charges will induce a separation of charge on the copper sphere. This is acceptable, provided they also mention that this results in no movement of the copper sphere.