Question

two conducting spheres of equal size have a charge of -3C and 1C respectively. A conducting wire is connected from the first sphere to the second. What is the new charge on each sphere

Answer 1

f 1 = 9×10^9 200×10^-6%R^2 and F 2 = -9×10^9 × 10^-6% R^2 now divide F1 and F2 then you will get 4 the option ; CONCEPT behind it is when two charges are attached then they will get same charge as -20+10= -10 C

Answer 2

Answer:

1) At the conductor surfaces, the tangential electric field is zero in equilibrium (otherwise charge would flow). The normal field need not be zero.

Zero tangential field is equivalent to the surface being an equipotential. (Potential is, after all, the line integral of the field (times -1).) The fact that the conductors have the same potential really does tell us that the field which drives charges is zero, and vice versa. If the tangential field is not zero, charges will flow until it is, or equivalently until the surface is an equipotential.

2) Note that a smaller sphere requires less charge than a larger one to achieve the same potential (you can see this by integrating the field from infinity for the two cases). The wire is really small (in radius), and needs correspondingly even less charge. In the limit of a 0 radius wire, the required charge goes to 0.

Differing charges do not necessarily imply different potentials. The capacitance, which depends on the geometry, gives the constant of proportionality between charge and potential. It's different for different shapes, so, at equal potentials, different shapes will contain different charges.

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