Electronics and Communication Engineering - Networks Analysis and Synthesis

16.
A capacitor used for power factor correction is single phase circuit decreases
power factor
line current
both line current and p.f.
the line current and increases p.f.
Answer: Option
Explanation:

Capacitor is used to improve (increase) p.f. Therefore, line current is decreased for the same active power.


17.
Evaluate the value of 2 [u (t - 1) - u (1 - 2t)] (u ( t + 1) + u (t)) at t = 3 sec.
0
4
1
Answer: Option
Explanation:

2[u(2) - u(1 - 6)] [u(4) + u(3)] 2 [1 - 0] [1 + 1] 4.


18.

Assertion (A): In an R-L circuit having high inductance, the rise of current is very slow.

Reason (R): The time constant of R-L circuit is L/R.

Both A and R are true and R is correct explanation of A
Both A and R are true and R is not the correct explanation of A
A is true but R is false
A is false but R is true
Answer: Option
Explanation:

A high value of time constant results in slow rise of current.


19.
The distance between the plates of a parallel plate capacitor is d. The dielectric is in two parts, each of equal thickness but dielectric constants ∈1 and ∈2 respectively. The total capacitance will be proportional to
1 - ∈2
12
Answer: Option
Explanation:

The combination is equal to two capacitors in series.

Hence, .


20.
An air cored coil has an inductance of 0.3 H. If another coil has an iron core of μr = 500, the remaining quantities being the same, the inductance of the second coil will be
0.3 H
0.3 x 500 H
none of the above
Answer: Option
Explanation:

Inductance a μr.