Solved Example: 9927-01

Magnetic permeability is maximum for ______ material. (TANGEDCO AE ME 2015)

A. Diamagnetic

B. Paramagnetic

C. Ferromagnetic

D. None of the above

Correct Answer: C

Solved Example: 9927-02

The relative permeability of a ferromagnetic material is: (UPPCL JE Feb 2018 Shift II)

A. Less than one

B. More than one

C. More than 10

D. More than 100 or 1000

Correct Answer: D

Solved Example: 9166-01

White noise is characterized by: (UPPSC Polytechnic Lecturer Electronics Mar 2022 Paper II)

A. Gaussian probability density function

B. Power spectral density. $\dfrac{\eta}{2} \delta(f)$

C. Autocorrelation function depends only on delay $\tau$

D. Autocorrelation $\dfrac{\eta}{2} \delta(\tau)$

Correct Answer: D

Solved Example: 9166-02

Which type of noise is produced in a microwave tube due to random nature of emission and electron flow? (UPPCL JE EC Mar 2021 Shift I)

A. Rutherford noise

B. Partition noise

C. Shot noise

D. Becquerel noise

Correct Answer: C

Solved Example: 9166-03

The white noise spectral density: (UPRVUNL AE Electronics and Instrumentation 2021)

A. Changes with frequency

B. Remains constant

C. Changes with BW

D. Changes with amplitude

Correct Answer: B

Solved Example: 9166-04

Following are few statements regarding noise in communication system:

a) Atmospheric noise, shot noise, solar noise are examples of external noise sources

b) Noise temperature is useful in dealing with UHF noise

c) Thermal agitation is the only source of noise in receiver

Choose the correct answer:

A. Only b)

B. a) and b)

C. b) and c)

D. a) and c)

Correct Answer: A

Solved Example: 9166-05

The noise caused by random variations in the arrival of electrons or holes at the output electrode of an amplifying device: (ISRO (VSSC) Tech Asst Electronics 2018)

A. White noise

B. Flicker

C. Shot Noise

D. Transmit time noise

Correct Answer: C

Solved Example: 9166-06

Spectral density of the white noise is: (URSC (ISRO) Tech Asst (Electronics): Aug 2017)

A. Uniform

B. Exponential

C. Gaussian

D. Poisson

Correct Answer: A

Solved Example: 9166-07

One of the following types of noise assumes importance at high frequncies: (SDSC (ISRO) Tech Asst (Electronics): April 2018)

A. Thermal noise

B. Shot noise

C. Transit-time noise

D. Flicker noise

Correct Answer: C

Solved Example: 9926-01

Relate the dielectric strength of insulating material with its thickness. (UPRVUNL JE EE Oct 2021 Shift II)

A. Dielectric Strength = Breakdown voltage $\times$ Thickness of the dielectric

B. Thickness of the dielectric = Dielectric Strength * Breakdown voltage

C. Dielectric Strength = Breakdown voltage / Thickness of the dielectric

D. Dielectric Strength = Thickness of the dielectric / Breakdown voltage

Correct Answer: C

Solved Example: 9926-02

What happens when moisture gets into the insulating materials? (UPPCL JE Electrical Sep 2021 Shift I)

A. It increases dielectric constant

B. It increases the insulation resistance

C. It increases the dielectric strength

D. It increases the dielectric loss

Correct Answer: D

Solved Example: 9925-01

Simens is the S.I unit of ________.

A. Conductivity

B. Conductance

C. Resistivity

D. Resistance

Correct Answer: B

Solved Example: 9925-02

The magnitude of current density in a superconductor depends on: (DFCCIL Executive Electrical 2016)

A. Temperature

B. Both temperature and magnetic field strength

C. Temperature for some time and then on magnetic field strength

D. Magnetic field strength

Correct Answer: B

Solved Example: 9925-03

With the rise of temperature, the conductivity of a semi-conductor: (Airforce Group X Jul 2021 Shift I)

A. Remains unchanged

B. Decreases

C. Increases

D. Nothing is certain

Correct Answer: C