Question 1 |
Consider the network graph shown in the figure. Which one of the following is
NOT a 'tree' of this graph ?


a | |
b | |
c | |
d |
Question 1 Explanation:
It is forming a closed loop. So it can't be a tree.
Question 2 |
The equivalent inductance measured between the terminals 1 and 2 for the circuit shown in the figure is


L_{1}+L_{2}+M | |
L_{1}+L_{2}-M | |
L_{1}+L_{2}+2M | |
L_{1}+L_{2}-2M |
Question 2 Explanation:

If current enters the dotte terminals of coil 1 then a voltage is developed across coil 2 whose higher potential is at dotted terminals.
\begin{aligned} V &=\frac{-M d I}{d t}+\frac{L_{1} d I}{d t}-\frac{M d I}{d t}+L_{2} \frac{d I}{d t} \\ &=\left(L_{1}+L_{2}-2 M\right) \frac{d I}{d t}\\ V&=L_{e q} \frac{d I}{d t} \end{aligned}
Question 3 |
The circuit shown in the figure, with R=\frac{1}{3}\Omega ,L=\frac{1}{4}H and C = 3 F has input voltage v(t) = sin2t. The resulting current i(t) is


5 sin(2t + 53.1^{\circ}) | |
5 sin(2t - 53.1^{\circ}) | |
25 sin(2t + 53.1^{\circ}) | |
25 sin(2t - 53.1^{\circ}) |
Question 3 Explanation:
\begin{aligned} i(t)=& V(t), Y \\ Y=& V(t)\left[\frac{1}{R_{1}}+\frac{1}{j \omega L}+j \omega C\right] \\ =& \sin 2 t\left[3+\frac{4}{2 j}+j \times 2 \times 3\right] \\ =& \sin 2 t[3-2 j+6 j]=\sin 2 t[3+4 j] \\ =& 5 \sin 2 t \angle \tan ^{-1} \frac{4}{3}=5 \sin \left(2 t+53.1^{\circ}\right) \end{aligned}
Question 4 |
For the circuit shown in the figure, the time constant RC = 1 ms. The input voltage is v_{i}(t)=\sqrt{2}sin10^{3}t. The output voltagev_{o}(t) is equal to


sin(10^{3}t-45^{\circ}) | |
sin(10^{3}t+45^{\circ}) | |
sin(10^{3}t-53^{\circ}) | |
sin(10^{3}t+53^{\circ}) |
Question 4 Explanation:
\begin{aligned} v_{0}(t)&=\frac{\frac{1}{j \omega C}}{R+\frac{1}{j \omega C}}\; v_{i}(t)=\frac{1}{1+j \omega C R} \sqrt{2} \sin 10^{3} t \\ &=\frac{1}{1+j \times 10^{3} \times 10^{-3}} \sqrt{2} \sin 10^{3} t \\ v_{0}(t) &=\sin \left(10^{3} t-45^{\circ}\right) \end{aligned}
Question 5 |
For the R - L circuit shown in the figure, the input voltage v_{i} (t) = u(t). The current i(t) is




a | |
b | |
c | |
d |
Question 5 Explanation:
\begin{aligned} I(s)&=\frac{V(s)}{s+2}=\frac{1}{s(s+2)} \\ I(s)&=\frac{1}{s(s+2)}=\frac{1}{2}\left[\frac{1}{s}-\frac{1}{s+2}\right] \\ i(t)&=\frac{1}{2}\left(1-e^{-2 t}\right) \\ \text { At } \quad t&=0, i(t)=0 \\ t&=\infty, i(t)=0.5 \\ t&=\frac{1}{2}, i(t)=0.31 \end{aligned}

Graph (c) satisfies all conditions .

Graph (c) satisfies all conditions .
Question 6 |
The impurity commonly used for realizing the base region of a silicon n - p - n transistor is
Gallium | |
Indium | |
Boron | |
Phosphorus |
Question 7 |
If for a silicon npn transistor, the base-to-emitter voltage (V_{BE}) is 0.7 V and the collector-to-base voltage (V_{CB}) is 0.2 V, then the transistor is operating in the
normal active mode | |
saturation mode | |
inverse active mode | |
cutoff mode |
Question 8 |
Consider the following statements S1 and S2.
S1 : The \beta of a bipolar transistor reduces if the base width is increased.
S2 : The \beta of a bipolar transistor increases if the dopoing concentration in the base is increased.
Which remarks of the following is correct ?
S1 : The \beta of a bipolar transistor reduces if the base width is increased.
S2 : The \beta of a bipolar transistor increases if the dopoing concentration in the base is increased.
Which remarks of the following is correct ?
S1 is FALSE and S2 is TRUE | |
Both S1 and S2 are TRUE | |
Both S1 and S2 are FALSE | |
S1 is TRUE and S2 is FALSE |
Question 8 Explanation:
\beta=\frac{I_{C}}{I_{B}}=\frac{\alpha}{1-\alpha}
When base width increases, recombination in base region increases and \alpha decreases and hence \beta decreases.
If doping in base region increases , then recombination in base increases and \alpha decreases, thereby decreasing \beta.
When base width increases, recombination in base region increases and \alpha decreases and hence \beta decreases.
If doping in base region increases , then recombination in base increases and \alpha decreases, thereby decreasing \beta.
Question 9 |
An ideal op-amp is an ideal
voltage controlled current source | |
voltage controlled voltage source | |
current controlled current source | |
current controlled voltage source |
Question 10 |
Voltage series feedback (also called series-shunt feedback) results in
increase in both input and output impedances | |
decrease in both input and output impedances | |
increase in input impedance and decrease in output impedance | |
decrease in input impedance and increase in output impedance |
There are 10 questions to complete.