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Q1. | A power transistor dissipates 5 W. If ambient temperature is 30° and case to air thermal resistance is 10° C/W, the case temperature is |

A. | 80°C [Correct Answer] |

B. | 20°C [Wrong Answer] |

C. | 32°C [Wrong Answer] |

D. | 305°C [Wrong Answer] |

View Answer
Explanation:-
Answer : ADiscuss it below :!! OOPS Login [Click here] is required to post your answer/resultHelp other students, write article, leave your comments |

**Also Read Similar Questions Below :**

⇒ Hue of a colour means

amount of light energy received by eye

predominant spectral purity of colour light

amount of other colours present

none of the above

⇒ A single phase half wave rectifier circuit has a free wheeling diode. The free wheeling diode will conduct only if

load is purely resistive

load is purely inductive

load is combination of R and L

load is purely inductive or combination of R and L

⇒ Find I for circuit shown b

0.125

0.0416666666666667

0.0833333333333333

0

⇒ The load end of a quarter wave transformer gets disconnected thereby causing an open-circuited load. What will be the input impedance of the transformer?

Zero

Infinite

Finite and Positive

Finite and Negative

⇒ An ac circuit has two branches in parallel. The impedances of the two branches are equal. The p.f. of one branch is 0.8 lagging and 0.8 leading. The overall p.f. is

zero

0.5 lagging

1

0.7 lagging

⇒ A circular polarizer converts a linearly polarized wave into a circularly polarised wave.

TRUE

FALSE

⇒ Pressing a key on telephone set generates two frequencies. The basis for selection of these frequencies is

the harmonics of one frequency should not be mistaken for the other frequency

the audio input to the handset transmitter should not be mistaken for a key pressing

both (a) and (b)

neither (a) nor (b)

⇒ How many cascaded stage of CE amplifiers will result in polarity inversion of the input signal?

Two

Three

Four

None

⇒ Which of these are 16 bit microprocessors?

80286

MC68000

Z8000

All

⇒ The maximum usable frequency for the 'E' layer is 10 MHz.

TRUE

FALSE

⇒ Consider the following network func

zero at origin

zero at infinity

pole at origin

pole at infinity

⇒ Maximum efficiency of class B power amplifier is 50%.

TRUE

FALSE

⇒ The kinetic energy of free electrons in a metal is (where

*k*is the de-Broglie wave number of the electron)

inversely proportional to

*k*

inversely proportional to square of

*k*

proportional to

*k*

proportional to the square of

*k*

⇒ A capacitor whose capacitance C

_{t}= C

_{0}(1- cos ω

*t*) is fed by a sinusoidal voltage

*v*= V

_{0}sin ω

*t*. The equation for current

*i*is

ω C

_{0}V

_{0}cos ω

*t*

ω C

_{0}V

_{0}sin ω

*t*

ω C

_{0}V

_{0}(cos ω

*t*- cos

^{2}ω

*t*)

none of the above

⇒ Virtual height of an ionospheric layer is always greater than its actual height.

TRUE

FALSE

⇒ Three resistance of 15 Ω each are connected in delta. The resistance of equivalent star will have a value of

15 Ω

5 Ω

5/3 Ω

45 Ω

⇒ A CB amplifier has

*r*

_{e}= 6 Ω, R

_{L}= 600 Ω and a = 0.98. The voltage gain is

100

600 x 0.98

98

6

⇒ The device having highest photo sensitivity is

photoconductive cell

photovoltaic cell

photodiode

phototransistor

⇒ In communication satellites, the up-link normally operates at a higher frequency than the down-link because it

gives a narrow beam shining into space

results in lesser signal attenuation

gives better beam-shaping

is easier to polarize a high frequency beam

⇒

**Assertion (A):** Magnetic susceptibility of copper is -0.5 x 10^{-5}.

**Reason (R):** Copper is diamagnetic material.

Both A and R are true and R is correct explanation of A

Both A and R are true but R is not correct explanation of A

A is true but R is false

A is false but R is true

⇒ A pulse train can be delayed by a finite number of clock periods by using

serial in-serial out shift register

parallel in serial out shift register

serial in-parallel out shift register

parallel in parallel out shift register

⇒ In 8085 microprocessor, what is the length of temporary register?

6 bits

8 bits

12 bits

16 bits

⇒ Evaluate the power stored in inductor and capac

25 J, 12.5 J

12.5 J, 25 J

25 J, 50 J

12.5 J, 50 J

⇒ Generally a VCR has

four stationary video heads

two stationary video heads

four rotating video heads

two rotating video heads

⇒ For a series R-L-C circuit, the characteristic equation is given

critically damped

underdamped

undamped

overdamped

⇒ A point charge of 6 μC is located at the origin, uniform line charge density of 180

*n*C/

*m*of 8

*m*length lies along the

*x*axis and a uniform sheet of charge equal to 25

*n*C/

*m*

^{2}of area p x 4

^{2}lies in the

*z*= 0 plane. Calculate total electric flux leaving the surface of sphere of 4

*m*radius centered at origin.

86.97 μC

8.697

*n*C

8.697 μC

86.97

*n*C

⇒ A shift register can be used for all of the following EXCEPT

ring counter

A/D conversion

series to parallel conversion

generation of delay

⇒ Which of the following form of angle modulation in this? If

*e*= 10 sin(10

^{8}

*t*+ 3 sin 10

^{4}

*t*)

AM

FM

AM or FM

AM or PCM

⇒ The carrier frequency will be if L = 50 µH and C = 1 nF.

512

612 kHz

712 kHz

812 kHz

⇒ The percentage saving in power of 100% modulated suppressed carrier AM signal is

100

75

66.6

50