# ECE - Questions and solutions set-3

Electronics and communication Engineering Questions and solutions set-3
Question:-
Option (A)
3/8
Option (B)
2/15
Option (C)
15/28
Option (D)
1/2
Correct Option:
C
Question Solution:
Let A is probability for Black
B is probability for Red
Probability of Black Black Red = 5/8 x 4/7 x 3/6 = 5/28
Probability of Black Red Black = 5/8 x 3/7 x 4/6 = 2/28
Probability of Red Black Black = 3/8 x 5/7 x 4/6 = 5/28
So Total Probability of getting 2-black ball is = 5/28 + 5/28 + 5/28 = 15/28
Question:-
Option (A)
A series combination of R1 and Parallel combination of R2 & C
Option (B)
A Parallel combination of R1 and Series combination of R2 & C
Option (C)
A series combination of R and Parallel combination of R & C
Option (D)
A parallel combination of R and series combination of R & C
Correct Option:
C
Question Solution:
at t = 0, voltage will be R, and at t = ¥ it will be 2R, hence condition is full – filled.
Because at t=0 capacitor is short circuited so voltage across current source will be R only
But at t = ¥ capacitor will be open circuited and hence total drop will be 2R only.
Question:-
Option (A)
RXX(t)
Option (B)
a+RXX(t)
Option (C)
a2+RXX(t)
Option (D)
a2+2a+RXX(t)
Correct Option:
C
Question Solution:
RYY(t) = E[Y(t) Y(t + t)]
= E[(a + X(t) (a + X(t + t)]
= E[a2 + a X(t + t) + a X(t)]
+[X(t). X(t + t)]
= a2 + aE[X(t)] + aE[X(t + t)] + RXX(t)
= a2 + RXX(t) Because X is a signal with zero mean
Question:-
Option (A)
0 ohm
Option (B)
25 ohm
Option (C)
50 ohm
Option (D)
100 ohm
Correct Option:
B
Question Solution:
Zi=(Z20/ZR) =(50)2/100 = 25 ohm
Question:-
Option (A)
Schottky TTL
Option (B)
TTL
Option (C)
ECL
Option (D)
C MOS
Correct Option:
D
Question Solution:
CMOS has most of the advantage except speed .Highest Noise margin is in HTL but after that it is CMOS. CMOS has the lowest power dissipation