Electronics questions - help needed

[logearav]

Electronics questions -- help needed

Homework Statement

Revered members,
I list below some of the questions asked in a competitive exam to test the proficiency of electronics. I request the members to give the answers. I have produced the answers which i have written, below each question. I require your help in ascertaining if they are correct.
An oscillator differs from an amplifier , because it
a) has more gain b) requires no input signal c) requires no DC supply d) always has the same input
Ans: requires no input signal
Which of the following devices has the highest input impedance
a) JFET b) MOSFET C) Crystal Diode d) Ordinary transistor
Ans : Ordinary Transistor
Which of the following is not a characteristic of UJT
a) Saturation Current b) Negative Resistance c) Peak point Voltage d) Bilateral Conduction
Ans : Saturation Current
A zener diode is destroyed if it
a) is forward biased b) is reverse biased c) carries more than the rated current d) carries less than the rated current
Ans : carries more than the rated current
In a full wave rectification, if the input frequency is 50 Hz, then the output has a frequency of
a) 100 Hz b) 50 Hz c) 25 Hz d) 200 Hz
Ans : 50 Hz
The multivibrator which generates square wave of its own is the -------- multivibrator
a) monostable b) astable c) bistable d) tristable
Ans : astable
The output impedance of a transistor is
a) high b) low c) infinity d) zero
Ans : zero
Revered members, I have reproduced the questions verbatim.

Homework Equations

The Attempt at a Solution

 

[vela]

You need to explain your thinking behind your responses.

 

[NascentOxygen]

It's a big call to state that the output impedance of anything is zero!