1. Which of the following is an example of amplitude scaling?

a) Electronic amplifier

b) Electronic attenuator

c) Both amplifier and attenuator

d) Adder

Explanation: Amplitude scaling refers to multiplication of a constant with the given signal.

It is given by y (t) = a x (t). It can be both increase in amplitude or decrease in amplitude.

2. Resistor performs amplitude scaling when x (t) is voltage, a is resistance and y (t) is output current.

a) True

b) False

Explanation: The given statement is not true. The relation between voltage, current and resistance is given by V = IR. Comparing with equation y (t) = a x (t), we can see that y (t) is the output voltage for given current x (t) with resistance R.

3. Which of the following is an example of physical device which adds the signals?

a) Radio

b) Audio mixer

c) Frequency divider

d) Subtractor

Explanation: Audio mixer is a device which combines music and voice signals. It is given by Y (t) = x1 (t) + x2 (t).

4. AM radio signal is an example for __________

a) y (t) = a x (t)

b) y (t) = x1 (t) + x2 (t)

c) y (t) = x1 (t) * x2 (t)

d) y (t) = -x(t)

Explanation: AM radio signal is an example for y (t) = x1 (t) * x2 (t) where, x1 (t) consists of an audio signal plus a dc component and x2 (t) is a sinusoidal signal called carrier wave.

5. Which of the passive component performs differentiation operation?

a) Resistor

b) Capacitor

c) Inductor

d) Amplifier

Explanation: Inductor performs differentiation. It is given by y (t) = L d/dt i(t) where, I (t) denotes current flowing through an inductor of inductance L.

6. Which of the component performs integration operation?

a) Resistor

b) Diode

c) Capacitor

d) Inductor

Explanation: Capacitor performs integration. V (t) developed across capacitor is given by

v (t) = (1/C)* ∫

^{t}

_{-∞}i (∂).d∂, I (t) is the current flowing through a capacitor of capacitance C.

7. Time scaling is an operation performed on _______

a) Dependent variable

b) Independent variable

c) Both dependent and independent variable

d) Neither dependent nor independent variable

Explanation: Time scaling is an example for operations performed on independent variable time.

It is given by y (t) = x (at).

8. Y (t) = x (2t) is ________

a) Compressed signal

b) Expanded signal

c) Shifted signal

d) Amplitude scaled signal by a factor of 2

Explanation: By comparing the given equation with y (t) = x (at) we get a=2. If a>1 then it is compressed version of x (t).

9. Y (t) = x (t/5) is _______

a) Compressed signal

b) Expanded signal

c) Time shifted signal

d) Amplitude scaled signal by factor 1/5

Explanation: y (t) = x (at), comparing this with the given expression we get a = 1/5. If 0<a<1 then it is expanded (stretched) version of x (t).

10. In discrete signal, if y [n] = x [k*n] and k>1 then ______

a) Some samples are lost from x [n]

b) Some samples are added to x [n]

c) It has no effect on samples

d) Samples will be increased with factor k

Explanation: For discrete time signal y [n] = x [k*n] and k>1, it will be compressed signal and some samples will be lost. The samples lost will not violate the rules of sampling theorem.