Help with ISRO 2012 electronics exam questions

[dexterdev]

I have a multiple choice question paper from ISRO 2012.

http://www.isro.org/pdf/EC-2012.pdf

Can I post doubtful questions in this thread. Is there someone to help me.

-Devanand T

 

[berkeman]

I have a multiple choice question paper from ISRO 2012.

http://www.isro.org/pdf/EC-2012.pdf

Can I post doubtful questions in this thread. Is there someone to help me.

-Devanand T

I think as long as you post about just one question at a time, and list the Relevant Equations and show your sincere Attempt at a Solution, it should be okay to do for now.

 

[dexterdev]

Thank you sir, I will do that..

 

[berkeman]

Which question do you want to tackle first?

 

[dexterdev]

The circuit diagram is shown in the attached file..q18

The question 18 is regarding harmonics of current wave in the ac circuit having diodes.

My answer if option (a) , any mistake here..

 

[NascentOxygen]

The question 18 is regarding harmonics of current wave in the ac circuit having diodes.

My answer if option (a) , any mistake here..

I don't think we can assume ideal or idealized diodes here, for the simple reason that if the source is an ideal sinusoid, and the diodes were to drop a fixed 0.6V, then where does the remainder of the voltage disappear?

So I picture operation over the diode's exponential curve (which extends to infinity), and giving rise to a distorted alternating current (perhaps missing a portion around the zero crossings).

Being a distorted sinewave, it contains harmonics.

 

[dexterdev]

Ok thankyou sir , will come with other doubts in the same paper..

 

[NascentOxygen]

Ok thankyou sir , will come with other doubts in the same paper..

I haven't answered the question, apart from ruling out (a).

 

[dexterdev]

sorry

 

[dexterdev]

As diode is having a nonlinear behaviour can we say the output is like
I = a + b v^1 + c v^2 + d v^3 + ....

so will all harmonics come...

 

[NascentOxygen]

As diode is having a nonlinear behaviour can we say the output is like
I = a + b v^1 + c v^2 + d v^3 + ....

so will all harmonics come...

I don't think so. I think you should try to sketch the expected current waveform.

 

[dexterdev]

ok I will try.

 

[dexterdev]

7th question

Hi pf,
Please see the attached figured , it is the 7th question.