Electronics and Communication Engineering - Networks Analysis and Synthesis

21.
In the circuit of figure the current through 5 Ω resistance at t = 0+ is
0 A
10 A
6.67 A
5.1 A
Answer: Option
Explanation:

Current through inductance is zero. Current through 5 ohm resistance = A.


22.
In an R-L circuit excited by a battery of voltage E, the current and voltage across resistor are 1- e-t and 2(1 - e-t) respectively. If there were an initial current of 2 A in the inductance, the voltage across resistance would have been
1 - e-t
2 - 2e-t
2 + 2e-t
4 - 4e-t
Answer: Option
Explanation:

From the given data R = 2Ω, L = 2H and E = 2V. Because of initial current of 2A, i(t) = 1 - e-t + 2e-t = 1 + e-t. Therefore, VR = 2(1 + e-t).


23.
Stray capacitance is important at low frequencies.
True
False
Answer: Option
Explanation:

At high frequencies the reactances of stray capacitance is small. Therefore stray capacitance assumes importance at high frequencies.


24.
A non-linear element has zero resistance.
True
False
Answer: Option
Explanation:

A non-linear element has a resistance which depends on the magnitude of current.


25.
In a RL circuit, the angle, θ by which the current lags the voltage is
0 > θ > - 90°
90°
0 < θ < 90°
Answer: Option
Explanation:

In RL circuit the current lags the voltage by an angle which is greater than 0° but less than 90°.