An infinitely long uniform solid wire of radius a carries a uniform dc current of density $$\widehat{\mathrm j}$$.

A hole of radius b (b < a) is now drilled along the length of the wire at a distance d from the center of the wire as shown below.

The magnetic field inside the hole is

In the circuit shown

The source of a silicon (n_i = 10¹⁰ per cm³) n - channel MOS transistor has an aewa of 1 sq $$\mu m$$ and a depth of 1 $$\mu m$$ . If the dopant density in the source is 10¹⁹/cm³, the number of holes in the source region with the above volume is approximately

In the three dimensional view of a silicon n-channel MOS transistor shown below, $$\delta = 20$$ nm. The transistor is of width 1 $$\mu m$$. The depletion width formed at every p-n junction is 10 nm. The relative permittivities of Si and SiO₂, respectively, are 11.7 and 3.9, and $${\varepsilon _0}$$ = 8.9 $$ \times {10^{ - 12}}$$ F/m.

The source-body junction capacitance is approximately