## An indian multiple choice exam similar to PGRE

ali8
Posts: 100
Joined: Sat Aug 29, 2009 8:20 am

### An indian multiple choice exam similar to PGRE

Hello,

While searching for positronium bending energy ( ), I came across this test.

http://csirhrdg.res.in/ps_mp.pdf

It's called CSIR NET Physical Sciences.

The exam should be 65 questions, but the pdf starts from question 21...

I found the questions somewhat similar to that of the PGRE, except for

the mathimatical questions, which IMHO are overkill.

Now, our indian friends in the forum probably know more about the test, and

if there are solutions to it (who knows!)

CarlBrannen
Posts: 381
Joined: Mon May 24, 2010 11:34 pm

### Re: An indian multiple choice exam similar to PGRE

Here's a start. This part took me a half hour:

21.4
22.1
23.2
24.2
25.4 This depends on choice of reference frame.
26.4 (guess)
27.2
28.3 (guess)
29.3 (i.e. 1/3^2)
30.3/4 What you want is symmetrized (1) which is between answers (3) and (4).
31.1 This is badly written; I'd have wanted "total spin in z direction".
32.3 Consider what this looks like outside the sphere.
33.2 (guess, maybe 1, uh, I don't know)
34.2
35.1 For small d, this becomes an electric dipole interaction => decreases
36.3 or maybe 2, I get the signs wrong
37.1 Isn't it kB/2 for each degee of freedom?
38.2 (Total Complete Guess)
39.4 The circuit is wrong because it has a gain of -33K/1K = -33. Thus the output will be severely clipped. But I think they're looking for (4) as the answer as it does note that the output will be inverted, amplified and linear. (Or linear for part of the cycle anyway). He probably meant to have a 3.3K/1K or 33K/10K for the resistors.
40.4
Last edited by CarlBrannen on Sat Jul 09, 2011 4:11 pm, edited 1 time in total.

ali8
Posts: 100
Joined: Sat Aug 29, 2009 8:20 am

### Re: An indian multiple choice exam similar to PGRE

Thanks CarlBrannen.

For 37, I thin it's 2, not 1.

As for 39, I believe the circuit is correct, look here:
http://www.electronics-tutorials.ws/opamp/opamp_2.html

We would like others to post solutions / comment / share

CarlBrannen
Posts: 381
Joined: Mon May 24, 2010 11:34 pm

### Re: An indian multiple choice exam similar to PGRE

ali8 wrote:As for 39, I believe the circuit is correct, look here:
http://www.electronics-tutorials.ws/opamp/opamp_2.html
If you want to find out what happens with that circuit hook one up. You will learn about something called "clipping". You will find that I am correct.

If that would take too long, then use the following simulation to find out what happens. Put the resistor values from the test into R_i=1K and R_f=33K, then slide the input voltage up and down. You will find that the circuit "saturates" at around 15 volts as the supply voltage is +/- 20 volts. For the circuit on the test, the supply voltage was +/- 5 volts and saturation will occur at around 4 to 5 volts (depending on the opamp type):
http://www.chem.uoa.gr/Applets/AppletOp ... Amps2.html

P.S. I've worked for 25 years as an electronics engineer.

ali8
Posts: 100
Joined: Sat Aug 29, 2009 8:20 am

### Re: An indian multiple choice exam similar to PGRE

CarlBrannen wrote:
ali8 wrote:As for 39, I believe the circuit is correct, look here:
http://www.electronics-tutorials.ws/opamp/opamp_2.html
If you want to find out what happens with that circuit hook one up. You will learn about something called "clipping". You will find that I am correct.

If that would take too long, then use the following simulation to find out what happens. Put the resistor values from the test into R_i=1K and R_f=33K, then slide the input voltage up and down. You will find that the circuit "saturates" at around 15 volts as the supply voltage is +/- 20 volts. For the circuit on the test, the supply voltage was +/- 5 volts and saturation will occur at around 4 to 5 volts (depending on the opamp type):
http://www.chem.uoa.gr/Applets/AppletOp ... Amps2.html

P.S. I've worked for 25 years as an electronics engineer.

Thanks for the site, it seems that you are right

niranjan
Posts: 9
Joined: Mon Sep 26, 2016 10:21 am

### Re: An indian multiple choice exam similar to PGRE

I think the answer for 26 is Option 2.
27. 1
28. 4
33. 1 [Look-up Standard books]