# What are the errors in JEE Main 9th April 2019 second shift?

#1

Has anyone spotted any errors in the jee main 9th april second shift??

Wrong questions that you are planning to challenge from JEE Main April 2019 (all shifts)?
#2

Q.14 is ambigous . One can interpret the question in a way that they want to compress spring using gas and they are asking internal energy of gas. In that case answer comes out to be option 2

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#3

@Aashish_Patel @Tushar_Rathore In Q.14 they can refer to the internal energy of the external agent which is doing work(and the heat is lost from the external agent while doing work) or the internal energy of the spring being compressed (where heat is lost from the spring). So, both 8 and -12 can be correct depending on interpretation of question. Right?

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#4

Shouldn't the answer to question 4 be 37.0? 5.29 has 3 significant figures.

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#5

Actually, even i chose 37.0 in haste. But it is wrong. Because, we are adding 5.29 7 times i.e
S= 5.29+5.29+5.29....(7 times)
By rules of addition number of decimal places in the operand containing the least number of decimal places must be taken significant(which are 2 in this case). Hence, answer for this question is 37.03 (2 decimal places).

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#6

I was waiting for many others to reply ,
According to me personally there are total of 4 questions wrong in this shift paper.

a) 3 in physics
b)1 in chemistry

PHYSICS SECTION-

As according to multiplication rule after multiplication the result must containe as many significant figures as the least significant figure among the two multiplicants {here 3 (5.29)} hence answer should also containe 3 significant figure s ie: 37.0

Clearly this ans is wrong as while finding electric field an extra term due to angle term cos(theta) Changes the whole ans and on satisfying the given condition D much greater than d answer comes to be option (3).

CHEMISTRY SECTION-

Correct option:(4)
As option (1) is correct but he is asking for in correct .the electron is given at a distance a● which means n=1
And Kinetic energy is inversely proportional to n^2 which means at least value of n {ie: 1 } Kinetic energy will be maximum hence it is correct.
In (4) electron is at distance of a● as n=1 is given and option says electron to be at a distance of 2a● which is obviously incorrect.

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#8

Bhai the answer of question 4 is 37.0 as it is given clearly in NCERT 1 pg 29 right column paragraph
We can't use addition rule for a multiplication operation ,as answer will be wrong

#9

But in NCERT it is written that the number of significant figures is kept the same not the number of decimal places. Reason : 5.29 is a measurement with a least count of 0.01. Thus the actual can be anything >= 5.285 and <5.295. If any of those numbers is multiplied by seven the 0.01 position digit will vary. But the digit in position 0.1 remains the same. Thus, you cannot be sure of the last 3 in 37.03. Thus the answer should have only upto 37.0

#10

The electron question is correct. It is saying 'total energy' not 'kinetic energy' (Total energy is -ve of kinetic energy). Also, who said electron cannot be found at 2a0. Electron can be found anywhere. The maximum probability to find it is at a0 (we describe the position of the electron by a probability distribution function). Welcome to the world of Quantum Mechanics!

#11

I would be more than happy if the answer is 37.0(because I have also marked 37.0). But still we need more thinking on this. I would like to know your teacher's opinion on this question as well.

#12

See he is clearly mentioning in the question 1s ie: n=1 it can't be some another value of n then how can electron be found at 2a0 (n=2) in this way I think option 4 is also incorrect.

#13

The point is that an electron that is found in 1s can be found at a distance 2a0 as well (See the probability distribution function for 1s orbital.) 1s orbital has no radial node(Node is a position where probability of finding an electron is 0 ). DO NOT MIX UP BOHR MODEL WITH QUANTUM MECHANICAL MODEL OF ATOM. Orbital and orbit are different.

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#14

Also 2a0 does not mean n=2.

#15

In the magnetic field of coil question, this is the graph of the current given in the original coil (not the induced one). Now, current induced depends on emf induced which depends on the negative of the rate of change of flux which depends on the current in the original coil. Thus current induced I' \propto -\frac{dI}{dt} where I is the original current. Now, we see that the current I increases up to a point and then decreases up to infinity. The region where it increases the derivative is positive, thus I' is negative. Then the derivative becomes negative and the current I' becomes positive. This corresponds to the answer given by NTA.

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#16

Did you challenge the significant figure question?

#17

Yeah, I did. Do you know what they will do, like will they send any message to me that they have considered it

#18

From the january experience, they do not inform anything whether they have accepted or not. You will get to know when they release the official final key. Moreover they did not refund the challenge fees even when the challenge was found correct.

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#19

are there any changes in our shift guys?? i havent saved my question paper so i cant find the codes..

#20

The significant figure one, 37.0 is given correct.

#21