LSA mid-1 bits

Unit-1


1. State variable approach can be applied to linear or nonlinear tine variant or tine
Invariant systems. ( TRUE )
2. The no. of state variables for a system will be equal to the _ORDER_ of the
Differential equation required to model it.
3. The state equation of a system is a function of ( C )
(a) State variables only (b) Present and past inputs only
(c) State variables and inputs (d) Present inputs & past inputs
4. In the RL network shown in fig. the transfer function i(s)/E(s) is given by ( C )
(a) R/R+SL (b) SL/R+SL (c) 1/R+SL (d) none
5. Electrical time constant of an armature controlled dc servo motor is ( b )
(a) Equal to mechanical time constant
(b) Smaller than mechanical time constant
(c) Longer than mechanical time constant
(d) None of the above
6. The system described by x1 = -x1 + x2; x2 = 2x – 3x2 will be ( a )
(a) Stable (b) Unstable but not Oscillatory
(c) Oscillatory (c) Marginally stable
7. Which input yields natural response? ( c )
(a) ac input (b) dc input (c) impulx input (d) ranp input
8. The state variable formulation of a system is given by the equations

The transfer function of the system is ( d )
(a) 1/(S+1)(S+3) (b) 1/(S+1) (c) 1/(S +3) (d) None




9. Given

The characteristic equation of the system is ( b )
(a) S3 + 20S2 + 24S + 9 = 0 (b) S3 + 9S2 + 24S + 20 = 0
(c) S3 + 24S2 + 9S +20 = 0 (d) None
10. The equivalent source method can’t be used on digital computer ( TRUE )


Unit-II

1, A non-sinusoidal periodic signal is generally referred to as sub-standard signal.
2. Which of the following represents average value of a non-sinusoidal periodic
Signal y(t) ( a )
(a) a = 1/T (b) a = 2/T
(c) a = 1/T (d) a = T.
3. If a signal is even signal then the trigonometric fouier series representation does not
contain __________ coefficient. ( b )
(a) a (b) b (c) both a and b (d) constant term
4. If a signal Y(t) exhibits half wave symmetry with a periodic 2П then which of the
following holds good . ( c )
(a) Y(t) = - y(t + 2П) (b) Y(t) = - y(t + П)
(c) Y(t) = y(t + 2П) (d) Y(t) = y(t + П)
5. Any periodic signal is a _power signal.
6. If Y(t) is a current or voltage signal then the energy in the signal is given by ( b )
(a) 1/t (b)
(c) 1/2t (d) None


7. A given function f(t) can be represented by a fourier series if it ( d )
a. is periodic b. is single valued
c. has a finite number of maxima and minima in any one period
d. all the above.
8. A periodic function f(t) is said to posses odd quarter-wave symmetry if ( d )
a. f(t)= f(-t) b. f(-t)= -f(t) c. f(t)=-f(t+T/2) d. Both b and c
9. in the case of a periodic function possessing halfwave symmetry , which fourier coefficient is zero. ( c )
a. an b. bn c. an d. none
10. which of the following periodic functions possesses even symmetry. ( a )
a. cos3t b. sin3t c. tcos5t d. (t+t2+t5)


Unit-III


1. Which of the following is know as ‘kernel’ ? ( c )
(a) x(t)dt (b) e jwtdt (c) e -jwtdt (d) None
2. Which of the following can be applied for both periodic and aperiodic signal? ( b )
(a) Fourier series (b) Fourier transforms (c) both a & b (d) none
3. The value of scaling factor in the definition of inverse Fourier transforms is
4. Fourier transforms is not defined for unstable signals
5. If Sincx = Sinx/x then the value of sinc(0) = __1_.
6. x(t (t-t0) = ________ . ( d )
(a) (t) (b) x(t) (c) (t0) (d) x(t-t0)
7. Which of the following is know as special density if x(t) X(w) ? ( a )
(a) 2 (b) (c) (d) 3



8. If Y(t) = t.e-2tu(t) then Y(w) = ___________. ( d )
(a) (b) (c) (d)
9. The discrete spectrum of ‘Fourier series’ is converted to continuous spectrum using
‘Fourier transforms ‘ ( true )
10. If Y(t) = e-2tu(t-2) then Y(w) = ( true )

Unit-IV

1. Which of the following is called neper frequency ? ( a )
(a) (b) W (c) S (d) P
2. The value of impulse function at t = 0 is _________ ( c )
(a) 1 (b) 0 (c) infinite (d) None
3. Convolution in one domain corresponds to __________ in other domain ( b )
(a) Convolution (b) Multiplication (c) Differentiation (d) Integration
4. The Convolution of any function with unit impulse function is ( c )
(a) Step signal (b) Ramp signal (c) Function it say (d) None
5. If x(t) = Sint and y(t) = Sint then find h(t) such that y(t) = x(t)h(t) ( b )
(a) u(t) (b) (t) (c) t.u(t) (d) 1
6. Laplace transform of A u(t) is _A_
7. The units of neper frequency are _____Neper /sec_____.
8. Z-transform has a value of 1 for impulse Signal ( true )
9. If the unit step response of a network is (1-e )u(t), then its unit impulse response will be ( a )
a. a e b. ae c. d. (1- a) e

10. impulse response of an RL circuit is a ( b )
a. rising exponential function b. decaying exponential function
c. step function d. parabolic function.