ECIL Previous Year Question Papers for ECE

Electronic and communication 2010

1.The current I in the given network.
a) 1A
b) 3A
c) 5A
d) 7A

2.For the Delta‐ Wye transformation in given figure, the value of the resistance R is.
a) 1/3 ohms
b) 2/3 ohms
c) 3/2 ohms
d) 3 ohms

3.In the given network, the Thevenin’s equivalent as seen by the load resistance Rl is
a) V=10 V, R= 2ohms
b) V=10V, R=3 ohms
c) V=15V, R= 2ohms
d) V=15V, R=3 ohms

4.The current I in a series R‐L circuit with R=10 ohms and L=20mH is given by i=2sin500t A. If v is the voltage across the R‐L combination then i
a) lags v by 45 degree
b) is in‐phase with v
c) leads v by 45
d) lags v by 90

5.In thr given network, the mesh current I and the input impedance seen by the 50 V source, respectively, are
a) 125/13 A and 11/8 ohms
b) 150/13 A and 13/8 ohms
c) 150/13 A and 11/8 ohms
d) 125/13 A and 13/8 ohms

6.A voltage sourcehaving a source impedance Z = R + jX can deliver maximum Average power to a load impedance Z, when
a) Z = R + jX
b) Z = R
c) Z = jX
d) Z = R –jX

7.In the given circuit, the switch S is closed at t=0. Assuming that there is no initial Charge in the capacitor, the current i(t) for t>0 is
a) V/R e^ (‐2t/RC)
b) V/R e^ (‐t/RC)
c) V/2R e^ (‐2t/RC)
d) V/2R e^ (‐t/RC)

8.For the circuit in given figure, if e(t) is a ramp signal, the steady state value of the Output voltage v(t) is
a) 0
b) LC
c) R/L
d) RC

9.For the series RLC circuit in given figure, if w=1000 rad/sec, then the current I (in Amperes) is
a) 2 ∟‐15
b) 2 ∟15
c) √2∟‐15
d) √2∟15

10.The Y‐parameter matrix (mA/V) of the two‐port given network is
a) [2 ‐1 ‐1 2]
b) [2 1 ‐1 2]
c) [1 ‐2 ‐1 2]
d) [2 1 1 2]

11.The maximum number of trees of the given graph is
a) 16
b) 25
c) 100
d) 125

12.Given figure shows a graph and one of its trees. Corresponding to the tree, the group of branches that CAN NOT constitute a fundamental cut set is
a) 1,2,3
b) 1,4,6,8,3
c) 5,6,8,3
d) 4,6,7,3

13.The Y‐parameter matrix of a network is given by Y=[1 1 ‐1 1] A/V. The Z11 parameter of the same network is
a) ½ ohms
b) 1/√2 ohms
c) 1 ohms
d) 2 ohms

14.For the given circuit, the switch was kept closed for a long time before opening it at t=0. The voltage v(0+) is
a) ‐10 V
b) ‐1 V
c) 0V
d) 10 V

15.The input impedance of a series RLC circuit operating at frequency W=√2w, w being the resonant frequency, is
a) R‐j(wL/√2) ohms
b) R+j(wL/√2) ohms
c) R‐j√2wL ohms
d) R‐j√2wL ohms

16.The threshold voltage V is negative for
a) an n‐channel enhancement MOSFET
b) an n‐channel depletion MOSFET
c) an p‐channel depletion MOSFET
d) an p‐channel JFET

17.At a given temperature, a semiconductor with intrinsic carrier concentration ni= 10 ^ 16 / m^3 is doped with a donor dopant of concentration Nd = 10 ^ 26 /m^3. Temperature remaining the same, the hole concentration in the doped semiconductor is
a) 10 ^ 26 /m^3
b) 10 ^ 16 /m^3
c) 10 ^ 14 /m^3
d) 10 ^ 6 /m^3}

18.At room temperature, the diffusion and drift constants for holes in a P‐type semiconductor
were measured to be Dp = 10 cm^2/s and µp = 1200 cm^2/V‐s, respectively. If the diffusion constant of electrons in an N‐type semiconductor at the same temperature is Dn = 20 cm^2/s, the drift constant for electrons in it is
a) µn = 2400 cm^2/V‐s
b) µn = 1200 cm^2/V‐s
c) µn = 1000 cm^2/V‐s
d) µn = 600 cm^2/V‐s

19.A common LED is made up of
a) intrinsic semiconductor
b) direct semiconductor
c) degenerate semiconductor
d) indirect semiconductor

20.When operating as a voltage regulator, the breakdown in a Zener diode occurs due to the
a) tunneling effect
b) avalanche breakdown
c) impact ionization
d) excess heating of the junction.