1. State whether the integrator system is stable or not.
a) Unstable
b) Stable
c) Partially Stable
d) All of the mentioned
Explanation: The integrator system keep accumulating values and hence may become unbounded even for a bounded input in case of an impulse.
2. For what values of k is the following system stable, y = (k2 – 3k -4)log(x) + sin(x)?
a) k=1,4
b) k=2,3
c) k=5,4
d) k =4,-1
Explanation: The values of k for which the logarithmic function ceases to exist, gives the condition for a stable system.
3. For a bounded function, is the integral of the odd function from -infinity to +infinity defined and finite?
a) Yes
b) Never
c) Not always
d) None of the mentioned
Explanation: The odd function will have zero area over all real time space.
4. When a system is such that the square sum of its impulse response tends to infinity when summed over all real time space,
a) System is marginally stable
b) System is unstable
c) System is stable
d) None of the mentioned
Explanation: The system turns out to be unstable. Only if it is zero/finite it is stable.
5. Is the system h(t) = exp(-jwt) stable?
a) Yes
b) No
c) Can’t say
d) None of the mentioned
Explanation: If w is a complex number with Im(w) < 0, we could have an unstable situation as well. Hence, we cannot conclude [no constraints on w given].
6. Is the system h(t) = exp(-t) stable?
a) Yes
b) No
c) Can’t say
d) None of the mentioned
Explanation: The integral of the system from -inf to +inf equals to a finite quantity, hence it will be a stable system.
7. Comment on the stability of the following system, y[n] = n*x[n-1].
a) Stable
b) Unstable
c) Partially Stable
d) All of the mentioned
Explanation: Even if we have a bounded input as n tends to inf, we will have an unbounded output. Hence, the system resolves to be an unstable one.
8. Comment on the stability of the following system, y[n] = (x[n-1])n.
a) Stable
b) Unstable
c) Partially Stable
d) All of the mentioned
Explanation: Even if we have a bounded input as n tends to inf, we will have an bounded output. Hence, the system resolves to be a stable one.
9. What is the consequence of marginally stable systems?
a) The system will turn out to be critically damped
b) The system will be an overdamped system
c) It will be a damped system
d) Purely oscillatory system
Explanation: The system will be a purely oscillatory system with no damping involved.
10. What is the other name of a Continuous Time Unit Impulse Function?
a) Dirac delta function
b) Unit function
c) Area function
d) Direct delta function
Explanation: The continuous time unit impulse function is also known as the Dirac delta function. This because it was first defined by Paul Adrein Maurice Dirac as ∂(t)=0.