ICTS, Banglore Physics Interview Experience - Chintan A.Patel | PAE blog

Greetings to fellow Physics Aspirants ,

             I am Chintan Patel from Pandit Deendayal Petroleum University and I would like to share my experience of interviews at one of the best research institutes in India i.e. ICTS-TIFR and TIFR Mumbai. This is my first blog post, so forgive me for any formatting errors.

     So, I was aware of this institutes from the 2nd year of my B.Tech(yes, I am a Mechanical Engineering student). I came to know that there is an exam called TIFR GS, which is conducted by TIFR all over India to shortlist candidates for Integrated Ph.D. (IPhd) and Ph.D. programme at TIFR and its sister institutes like ICTS, NCRA, and TIFR Hyderabad.

Preparation

              So, I started preparing for this exam when I was in 3rd year of my B.Tech. The only difficulty in preparation was that the syllabus of the exam is completely unknown. So I started solving previous year papers of GS. There were many topics which I hadn't even seen before like electronics, solid state physics, etc. So started making notes of basics of these topics. You don't need deep knowledge in these topics, just basic concepts are enough. So this way I was able to solve each and every question asked in previous papers. If you are preparing for any such entrance exam I suggest this loop method. You start with solving some paper if you find any topic which you are not quite good or unfamiliar, prepare for that topic and again solve some papers. I have tried this method in GATE and JEST and it is quite effective, but it takes time and determination.

Exam day

           9th December 2018: The day on which GS exam was taken nationwide. I was very nervous, since this was my first University entrance exam and getting admission to TIFR was my dream. The exam was a computer-based online exam. The difficulty level of questions was mediocre. There were some tough and some easy questions. I recommend solving all the easy questions first. It happens with me quite often that I get stuck to some tough question, and waste an ample amount of time in it. I suggest you not to do this. Solve the questions related to topics you are very familiar with first. There is negative marking in some questions, so be careful with those questions.
You might be thinking why I am writing about the exam tips here. But it's important as a head start.
So my exam went OK. I didn't expect to get an interview call. I was out of time. I couldn't solve all the questions. But then I realized, this happened to everyone. So I had some relief.

The results were supposed to be announced on 9th January, but there was a delay and the results were announced on 11th January. On the website, there was a PDF containing names of students shortlisted based on GS. There were about 100 candidates. And there was my name in there. I was very excited, until..... I read on the top 'Candidates shortlisted for written test 2'. I was baffled. This was the first time TIFR was going to conduct a written test. Candidates qualifying this test will be eligible to appear for the interview. But there was still no News on ICTS list. I knew that ICTS selects very few students for interview. But after some days, I got a mail from ICTS. ICTS was also going to take written test 2.

ICTS took the written test on 5th March and students qualified in the test were to give a personal interview on 6th March. TIFR took the test on 11th March and interview on 12th March.

The syllabus regarding these tests was not specified at all. Nothing was specified except the date of the test. The test was to be taken at respective campuses of TIFR and ICTS. So I brushed up the basics of core physics subjects like Quantum Mechanics(QM), Statistical Physics(SP), Classical Mechanics(CM), Mathematical Physics(MP), etc.

ICTS Bangalore experience

                            I reached Bangalore a day before the test. On the day of the test, bus service was arranged from IISC campus to ICTS. I was very nervous about the test. I didn't want to ruin this opportunity.

The test started on 5th March at 10 a.m. I could have uploaded the question paper, we were to return the paper with the answer sheets. So anyway, the test was of 3-hour duration. The test was of 100 marks. It contained 7 questions of 25 marks each. We were supposed to solve any 4 questions. The distribution of questions was as follows:

• Quantum Mechanics (2): 
• Both questions were pretty straightforward if you know basic QM like infinite well, finite step potential, normalization of a wavefunction, etc. I attempted both of them since QM is my favorite and strong subject.
• Classical Mechanics (2): 
• The 1st question contained sub-questions. One of them was to find the gravitational force on point object due to a circular ring. And then to find the point at which force is maximum. Then we were asked to find the polar equation of an orbit of a particle in some attractive potential. Attempted this one, It was a bit lengthy.
• 2nd question was related to modes of a vibrating string. We were to find wave speed, the total energy of oscillations, etc. didn't attempt.
• Statistical Physics: 
• I didn't attempt this one too. It was related to many particles in an infinite potential well. We were to find the expression of the partition function, heat capacity at a lower and higher temperature, etc.
• Electrodynamics: 
• I attempted this one. It was related to potential in a conducting shell. I don't exactly recall the question, so pardon me. But if you know the basics of conductors, you'll be able to solve this question.
• Fluid mechanics:
• I didn't even have a look at this question since I had already figured out my 4 favorite questions.

The result of the written test was published on 5th March at about 9 p.m. on the ICTS website. 7 candidates were shortlisted for Integrated Ph.D. and 24 candidates for Ph.D. interview. I was very happy that I was one of 7 candidates who were to give an interview for admission for IPhd on the next day.

The Interview

              6th March 2019: The interviews started at about 10 a.m. First, they took interviews with Ph.D. candidates, so my interview was after lunch.

My interview started at around 4 p.m. There were 3 faculties in the panel. Let's call them F1, F2, and F3.
F1 is a faculty at ICTS who is an expert in Theoretical Fluid Mechanics.
F2 is a faculty from IISC Bangalore who is an expert in observational astronomy.
F3 is a faculty at ICTS, an expert in Theoretical Condensed Matter Physics.

All 3 of the interviewers were very friendly. They offered me some snacks but I was too nervous to eat anything. First, they made me comfortable by introducing themselves.

F1 asked me the first question. The question was something like this:

There is some snowfall at a constant rate and there is a truck removing snow at some other constant rate. I was asked to find the time at which the snow started to fall. (Sorry but I can't recall exact question.)

Initially, I was confused. But I spoke out every thought coming to my mind loud. This is very important. During such interviews, if you don't know how to solve a problem, speak out your ideas aloud. This helps the interviewer to assess your thinking process and analytical skills. So anyway, after a few mistakes and hints, I derived a simple differential equation which can be solved to find the asked time.

Then F2 asked me a question related to a bulb. The question was like this:

There is a bulb whose power rating is 40 W. When we connect a multimeter across it, we get a resistance of some 50 ohms. The voltage across it is standard 220 V. Now if we apply the formula V^2/R, we get a power of around 968 W. But the rating of the bulb is 40 W. Where is that extra power going?

Initially, I was really confused. I tried to explain that some of the power goes into heating of the filament, but F2 argued that when a steady state is reached, temperature becomes constant. Then he made me look the equation again carefully. Then the bell rang in my head, the resistance measured with the multimeter is at room temperature. But when the temperature of the metal increases, its resistivity increases. Thus the denominator in the equation increases and power decreases. He seemed to be satisfied with the answer.

Then F3 asked me to

Find out the trajectory of a particle whose X and Y components of velocity were given as functions of x and y coordinates. 

It wasn't a tough equation to solve. I found that the trajectory was a set of hyperbolae.

Then F1 asked me to

Draw velocity profile of laminar and turbulent flow through a pipe.

 Luckily I drew the shapes correctly but I did a mistake in slopes of the profiles, which I corrected after some hints from F1.

Then F2 asked me this question:

What would happen to a balloon filled with Helium, tied in a car and if the car is given some acceleration? 

Luckily I had seen this question on Quora before, so I answered it correctly. If you know the answer to this, write in the comments section.

Then F3 asked me to

Write the Hamiltonian of a Harmonic oscillator.

 I wrote it on the board. Then he asked me, what would be the change if we apply a constant electric field in the x-direction.  I added an additional term. Then he asked me whether I can find the eigenstates and eigenvalues of this modified potential. I gave it some thought and realized that by adding and subtracting an additional term, I can make it look like a harmonic potential, but with different frequency and center of symmetry. He agreed with me.
Then he asked me to

Find the expectation value of dipole moment of an electron trapped in this particular potential.

 I did some lengthy calculation, but the answer turned out to be very simple. He then asked me to find the average deviation of dipole moment, if the system is at equilibrium at some temperature T. I found the deviation for some nth level, found the partition function and just spoke out how I would proceed. F3 was satisfied and asked me to stop since the calculations were too lengthy.  This was the last question. I took a deep breath of relaxation.
I returned home and prepared myself for the Mumbai interview.

Update: I got selected at ICTS for IPhD program.

You can proceed to read my Interview Experience at TIFR Mumbai

 Overall the interviews were really interesting. You get to solve some really cool problems and the interviewers are very friendly.

Thank you very much ,

Chintan A.Patel

About the author:

Mr. Chintan A.Patel has sucesfully cleared interviews of both ICTS, Banglore and TIFR, Mumbai and was offered Integrated PhD(Physics) in those institutes both of which are considered as State of the art Institutes in the country and are also well recognized Internationally



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