Is it necessary for parallel plate capacitors to have same plate areas? ?

Question

If we take two plates with different areas, one plate larger than other then what will happen? It should still store charge when connected to a battery. But how will we calculate the capacitance theoritically without experiments?


And if we take two plates of same area, and tilt one of them , then can we take the area components parallel and calculate the capacitance?

Answer 1

It is not necesary for the plates to be the same.

In fact, if you take ANY two conductors of ANY shape placed ANYWHERE with respect to each other, they will form a capacitor.

Parallel plate capacitor with plates of the same shape and area placed close to each other is most oftenly used configuration becuse
a) it's easy to achieve sufficiently large capacitances, and
b) such configuration reduces coupling with exteranal electric fields.

A capacitor with plates shifted with respect to each other will feel external electric field, i.e noise.

E ---> E ---> E ---> E ---> E ---> E --->
E ---> E ---> E ---> E ---> E ---> E --->

-q-q-q-q
------------------A------- A-------A--
. . . . . . . . .----A------- A-------A------------------
. . . . . . . . . . . . . . . . . . . . . . . . +q+q+q+q

E ---> E ---> E ---> E ---> E ---> E --->
E ---> E ---> E ---> E ---> E ---> E --->



Overlapping area A should be used in formula fro capacitance in all cases.

Answer 2

No, they can have different areas. But why would you want to? It would be a waste of material, unless the capacitor is an accidental capacitor, such as a circuit being too close to another conductor (like a housing wall).

You can look up the equations in any Electromagnetics or physics book.