Question

1. How does the ratio of the plate length (l) versus separation (d) affect the fringing effect at the edges of the plates?

Pattern C: Floating Electrode

2. How does the circular electrode distort the field?

3. What is the potential of the circular electrode? Of the area inside the electrode?

4. What effect would moving the circular electrode have?

Pattern D: Coaxial Cable

5. What is the field inside the inner conductor, between the two conductors, and outside the outer conductor?

Answer 1

1) Longer length(l) small seperation(d) will cause less fringing effect at the edge, so when the ratio of plate length and seperation is large enough then the fringing effect can be ignorable. If the ratio (l/d) is too small fringing effect is very much prominant.

Pattern C: Floating Electrode

2)So, here circular electrode is simillar to a hollow metal sphere between the capacitor plates.

3) Potential of the circular electrode will be equals to the potential of the center point of the electrode due to the parallel plates (we don't have data to provide numerical value). And the are inside the electrode will have the same potential i.e. equipotential surface.

4) If we move the circular electrode, the field line will be distorted differently with time and the region of zero field (inside electrode) will also changes. It will be attracted by lower potential plate and repelled by higher potential plate until it touches any plate.

Pattern D: Coaxial Cable

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