**Top Most Electronics Objective Questions Part – 2**

**1. Two coupled coils have L1 = 0.6 H, L2 = 0.6 H and coupling coefficient = 0.25 Coil 2 has 800 turns. If current I1, in coil I is 6 sin 100t amps, then the voltage across coil 2 is**

(a) 90 cos l00t volts

(b) 9 cos l00t volts

(c) 0.9 cos l00t volts

(d) 0.09 cos l00t volts

**Ans:-A**

**2. Cascading two amplifiers will result in**

(a) reduction in overall gain and increase in the overall bandwidth

(b) reduction in overall gain and reduction in the overall bandwidth

(c) increase in overall gain and increase in the. overall bandwidth

(d) increase in overall gain and reduction in the overall bandwidth

**Ans:-D**

**3. A tank circuit of R.F. amplifier has a coil of Q factor of 100. It is tuned to a frequency of 1 MHz. The bandwidth of the circuit is**

(a) 1 kHz

(b) 10 kHz

(c) 100 kHz

(d) 1000 kHz

**Ans:-B**

**4. An amplifier with an initial open-loop gain of 400 is used as a negative feed back amplifier. The feedback factor is 0.05. If the gain of the amplifier changes by 10% due to temperature, then the closed-loop gain will change approximately by**

(a) 0.05%

(b) 0.1%

(c) 0.5%

(d) l %

**Ans:-C**

**5. The gain and input resistance of an amplifier in a boot-strap sweep circuit are respectively**

(a) unity and zero

(b) infinity and infinity

(c) unity and infinity

(d) infinity and zero

**Ans:-C**

**6. Consider the following processes in the fabrication of ICs:**

1. Substrate

2. Oxide layer

3. Photo resist and photolithography

4. Etching

**The correct sequence of these processes is**

(a) 1,2,3,4

(b) 1,2,4,3

(c) 2,1,3,4

(d) 2,1,4,3

**Ans:-A**

**7. A bulb is controlled by two switches A and B. The bulb glows only when either switch A or switch B is ON. Its Boolean expression is**

(a) AB÷AB

(b) AB

(c) AB+AB

(d) AB÷AB

**Ans:-D**

**8. Open-collector gates requires**

(a) external output pull-up resistors

(b) external capacitor to ground

(c) a buffer at the output

(a) higher supply voltage

**Ans:-A**

**9. In microprocessor based system, DMA facility is required to increase the speed of data transfer between**

(a) microprocessor and I/O devices

(b) microprocessor and memory

(c) memory and I/O devices

(d) microprocessor, I/O devices and memory

**Ans:-C**

**10. The bandwidth of a PCM system having two quantization levels is B. If the quantization level is increased to 8, the resultant bandwidth will be**

(a) B

(b) 2B

(d) 3B

(a) 4B

**Ans:-C**

**11. Consider the following statements:**

**The total number of modes entering an optical fiber depends on**

1. core radius

2. wavelength of the optical source.

3. refractive index profile.

**Of these statements:**

(a) 1 and 2 are correct

(b) 2 and 3 are correct

(c) 1 and 3 are correct

(d) 1, 2 and 3 are correct

**Ans:-C**

**12. A video monitor uses 600 lines per frame and 40 frames per second. Each scan line has a maximum of 1000 pixels. To display on the monitor, the highest frequency of the signal required is**

(a) 24 MHz

(c) 6 MHz

(b) 12MHz

(d) 4MHz

**Ans:-A**

**13. In a pulse radar system, the received echo energy is inversely proportional to (R is the range measured)**

(a) (R) 1/4

(b) R2

(c) R3

(d) R4

**Ans:-A**

**14. The radio altimeter on board an aircraft is basically a**

(a) Doppler radar

(b) MTI radar

(c) Continuous wave radar

(d) Frequency modulated CW radar

**Ans:-D**

**15. The double integration of a unit step function will result**

(a) A unit step function

(b) Ramp function

(c) Impulse

(d) Parabola

**Ans:-D**

**16. Consider the following statements:**

**A circuit is said to be in resonance when the**

1. Current delivered by the source is in phase with the source voltage.

2. Load current is in phase with the load voltage.

3. Power factor of the circuit is unity.

**Of these statements:**

(a) 1 and 3 are correct

(b) 1 and 2 are correct 4

(c) 2 and 3 are correct

(d) l, 2 and 3 are correct

**Ans:-D**

**17. An antenna has radiation resistance of 30 ohm, equivalent resistance of 10 ohm for all other losses and directive gain of 4.0. The power gain of the antenna will be**

(a) 4.0

(b) 3.0

(c) 2.0

(d) 1.33

**Ans:-B**

**18. A dielectric material in an electric field gets polarized. If the polarization is non.-uniform, then there would be accumulation of**

(a) bound charge only on the surface

(b) bound charge only within the material

(c) bound charge within the material as well as on the surface

(d) free charge on the surface of the dielectric

**Ans:-C**

**19. Consider the following statements regarding negative feedback in a closed loop system:**

1. It increases sensitivity.

2. It minimises the effect of disturbance.

3. There is a possibility of instability.

4. It improves the transient response.

**Of these statements:**

(a) 1, 3 and 4 are correct

(b) 1, 2 and 4 are correct

(c) 1, 2 and 3 are correct

(d) 2, 3 and 4 are correct

**Ans:-D**

**20. Match List I with List II and select the correct answer using the codes given below in the lists:**

**List I (Loop transfer function)**

A. K(s+1) / s2(s+10)

B. K / s (s + 2) (s2 + 2s + 2)

C. K / s(s + 2) (s2 + 2s + 5)

D. K / s(s+4) (s2 +4s+5)

**List II**

** (Point(s) of root-locus plot)**

1. One real breakaway point

2. Two real breakaway points

3. Three real breakaway points

4. One real and one pair of complex conjugate break-away points

**Codes:**

**A B C D**

(a) 1 2 4 3

(b) 1 2 3 4

(c) 2 1 4 3

(d) 2 1 3 4

**Ans:-B**

**21. A system has a complex conjugate root pair of multiplicity two or more in its characteristic equation. The impulse response of the system will be**

(a) A sinusoidal oscillation which decays exponentially, the system is therefore stable

(b) A sinusoidal oscillation with time multiplier, the system is therefore unstable

(c) A sinusoidal oscillation which rises exponentially with time; the system is therefore unstable

(d) A dc term and harmonic oscillation, the system therefore becomes limiting stable

**Ans:-B**

**22. A lag compensation network**

(a) Increases the gain of the original network without affecting the stability

(b) Does not affect stability on increased gain

(c) Reduces the steady-state error

(d) Reduces the speed of response

**Ans:-C**

**23. A system G(s) is expressed in the state variable form as**

**X = JX + Bu**

** y = CX + Du**

** Consider the following statements with regard to the properties of Jordan canonical matrix J:**

1. The diagonal element of J is poles of G(s).

2. All the elements below the principal diagonal are zeros.

3. All the elements above the principal diagonal are zeros.

**Among these statements:**

(a) 1 and.3 are correct

(b) 1 and 2 are correct

(c) 2 alone is correct

(d) 3 alone is correct

**Ans:-B**

**24. A 0-300 V voltmeter has a guaranteed accuracy of 2 per cent of full-scale reading. If the voltage measured by this instrument is 180 V, then the limiting error will be**

(a) Less than 2%

(b) Less than 3% but greater than 2%

(c) Less than 4% but greater than 3%

(d) 4%

**Ans:-C**

**25. Which one of the following statements regarding Hay Bridge and Maxwell Bridge is correct?**

(a) Hay bridge is same as Maxwell Bridge having resistor R1 in parallel with C1 in one arm

(b) Hay bridge has R1 in series with C1 with Maxwell bridge has R1 in parallel with C1

(c) Hay bridge has R1in parallel with C1and Maxwell bridge has R1 in series with C1

(d) Hay bridge and Maxwell bridge are similar but Hay bridge is used to measure unknown capacitance while Maxwell bridge is used to measure unknown inductance

**Ans:-A**