Question

When a potential difference of 142 V is applied to the plates of a parallel-plate capacitor, the plates carry a surface charge density of 45.0 nC/cm2. What is the spacing between the plates?

Answer 1

Solution:::

The capacitance of the parallel -plate capacitor is given by

  

where C.......capacitance

A.........area of overlap of two plates

......... the electric constant  

d..........the spacing between the plates

On the other hand, the capacitance is given by

  

where q.....charge of one plate

U........ the potential difference between the plates

hence The charge may be expressed in terms of the surface charge density  

i.e  

so by Considering all the formulas above we have

Therefore the spacing between the plates is d=2.79micrometers