- #1

FS98

- 105

- 4

## Homework Statement

(a) Two long, thin parallel rods, a distance 2b apart, are joined by a semicircular piece of radius b, as shown in Fig. 1.44. Charge of uniform linear density λ is deposited along the whole filament. Show that the field E of this charge distribution vanishes at the point C. Do this by comparing the contribution of the element at A to that of the element at B which is defined by the same values of θ and dθ.

(b) Consider the analogous two-dimensional setup involving a cylinder and a hemispherical end cap, with uniform surface charge density σ. Using the result from part (a), do you think that the field at the analogous point C is directed upward, downward, or is zero? (No calculations needed!)

## Homework Equations

F = kq/d^2

## The Attempt at a Solution

I have no idea how to begin this problem. Can somebody explain to me where I can start? I imagine I have to use the equation above and find that the values from each part of the rods cancel out, but I don’t know how without knowing the charge in either case or the distance in the one case.