An Intrinsic semiconductor has 10^8 mobile electrons passing through a given point in 1second when connected across a 12 V d.c supply. Determine the:

 (I) Current in the material

Soln 

t = 1 sec

V = 12 v

1coulomb = 6.25 x 10^ 8 electrons

?                     10^ 8 electrons

  = (1 x 10^ 8 electrons)/(6.25 x 10^8)

    = 0.16 coulombs

Charge Q = current x time

 Current = charge (q)/time(t)

                = 0.16/1 sec

                = 0.16 amperes

(II) Power dissipated

Soln

Power(P) = I ^ 2 x R

            R  = V / I

                 = 12/0.16

                  = 75 ohms

Power dissipated = I ^2 R

                                 = 0.16^2 x 75

                                  = 1.92 Watts