Biology; Chemistry; Physics: Post your doubts here!

[Neil Shah]

Can someone pls. help me with question no 30 and 40 in tis paper? (5054_w11_qp_11.pdf)

 

[Neil Shah]

np


For 30:
A. The circuit would still work if the earth wire is not connected
B. Again the circuit would still work because The fuse would not bblow up as current is circuit is very low
C. Lamps can work on a.c too
D. The current move from live wire. when it is not connected, circuit would not work as no current would be present in the circuit
For 40:
U can use Fleming left hand law: Index finger pointing in the paper, middle finder opposite of direction of radioactive source and thumb finger to the left and the beta particles are deviated at shor distance as compared to alpha and gamma doesnot deviate

sorry Ally Emran, I did not quite understand the explanation to question 40 , could u explain it in simpler terms?

 

[usama321]

sorry Ally Emran, I did not quite understand the explanation to question 40

np


For 30:
A. The circuit would still work if the earth wire is not connected
B. Again the circuit would still work because The fuse would not bblow up as current is circuit is very low
C. Lamps can work on a.c too
D. The current move from live wire. when it is not connected, circuit would not work as no current would be present in the circuit
For 40:
U can use Fleming left hand law: Index finger pointing in the paper, middle finder opposite of direction of radioactive source and thumb finger to the left and the beta particles are deviated at shor distance as compared to alpha and gamma doesnot deviate

Well, Aly, the explanation for the question 40 is a bit different. When using the left hand rule, the thumb shows the direction of the movement of the ALPHA particles in magnetic field. It does not have to do with which particle deviates first. The alpha particle deviates in the direction of the thumb, and the beta particle deviates opposite to it, which clearly tells us the answer to the question

 

[usama321]

provided that the index finger is in the direction of the magnetic field, the middle finger in the direction of the moving particles, that is from top to down in this case

 

[usama321]

middle finger should be from down to top !?!?! i guess so

Nope, see the question again I think you are mixing the detector and the source
The easiest way to remember the movement of these particles in a magnetic field is to use either the left hand or right hand rule.

Using the right hand rule, while the index finger points towards the magnetic field, and the middle finger points to the direction of the movement of particles, the thumb would ALWAYS show the direction of the movement of alpha particles. Once we know the direction of alpha particles, we know that beta would deviate in the opposite direction. No worries about gamma

 

[usama321]

for thumb direction <----
for mid finger direction ^
|
for index one= inside the paper
USING LEFT HAND LAW! Actually i got the correct answer using this method!! Every time
Right Hand Rule is correct but it would create confusion especially for me :/

well, for everyone his own method

 

[usama321]

finished with o level this session..........waiting for results

 

[Neil Shah]

Ok Ally Emran and Usama321, what is going on? can someone pls explain it to me in simple terms!! (sorry a little slow in understanding physics )

 

[Neil Shah]

u know the fleming left hand rule?

yes, it is used to find the direction of force acting on a current carrying wire when a current carrying wire is placed in a magnetic field... and in the left hand rule, isn't the middle finger used to find the direction of current or is it used to find the "direction of the moving particles"?

 

[usama321]

yes, it is used to find the direction of force acting on a current carrying wire when a current carrying wire is placed in a magnetic field...

use the left hand rule here too, just for your own help

use the index finger to point into the paper, that is the direction of the magnetic field given in the question.
use the middle finger to point towards the direction of the particles, that is from top to bottom in this question
The direction of the thumb would now show you the direction of the movement of the alpha particles.
Now we know that in a magnetic field, the beta particles always move opposite to the alpha particles
Therefore we recognize the particles as beta particles

 

[Neil Shah]

but then, why can't the answer be alpha particles and also how is the direction of the particles from the top to the bottom? :/ do the particles move from radioactive source to detector?

OMG!!!! I just understood!!!! thanks so much Usama321 and Ally Emran... so what exactly is the principle/law used here called as aren't the left and right hand rules used for electromagnetic induction? And Usama321 , the right hand rule doesn't actually work for this-only left hand does- or do both work?

 

[Neil Shah]

Aly Emran usama321 ...You guys are amazing at Physics!!! Do u guys mind helping me with a few other doubts that I have? I would really appreciate if u guys could!!! I have linked the questions in the post below...

 

[Neil Shah]

All my MCQ doubts...
1. June 2007 Q.23
2.June 2008 Q.8
3.June 2008 Q.17
4.June 2008 Q.23
5.June 2008 Q.30
6. June 2010 paper 11 Q.34
7.June 2012 paper 11 Q.8
8. November 2012 paper 11 Q.3
9.November 2012 paper 11 Q.18
10.November 2012 paper 11 Q.26
Would really appreciate if any one could explain me the answers to these questions ASAP as I have an upcoming Physics test...

 

[usama321]

All my MCQ doubts...
1. June 2007 Q.23
2.June 2008 Q.8
3.June 2008 Q.17
4.June 2008 Q.23
5.June 2008 Q.30
6. June 2010 paper 11 Q.34
7.June 2012 paper 11 Q.8
8. November 2012 paper 11 Q.3
9.November 2012 paper 11 Q.18
10.November 2012 paper 11 Q.26
Would really appreciate if any one could explain me the answers to these questions ASAP as I have an upcoming Physics test...

FIRST OF ALL, pls post links to these papers the next time. Pls don't download and then upload.

1: this is a bit tricky.. The boy hears the first bang, and he hears the second bang 1 second after that. Now we know, that the sound for the second bang has to first hit the building and travel back to the girl, before continuing on towards the boy. This means that it travels 150 + 150 m = 300 m extra before reaching the boy. As there is an increase of 1s before this sound reaches the boy, and it travels an extra 300 m in that one second, it means that the speed was 300m/s

2: moment = force * perpendicular distance from pivot. QC is perpendicular distance

3: heat transfers from a region of higher temp to lower temp. Rest is pretty self explanatory

4: you have to use a ruler for this one, so that the two rays meet at the point shown on the paper, and continue the ray after the lens...........it would pass through the focal point.

5: current lowest when resistance highest, which is in series..............current highest when resistance lowest, which is in parallel circuit (you can set a resistance to these resistors and calculate the resistance just for your confirmation as this would stick in your head)

6: Current is reversed as the poles are changed on the coil. As it is now pulled out quickly rather than slowly, the current is higher

will answer the rest later..........m in a hurry...........and don't forget the links the next time

 

[Neil Shah]

usama321 Aly Emran Wow!!! U guys r just amazing at explaining! Is it ok if I ask u guys a few paper 2 and 4 doubts in the coming days (have got an upcoming pre mock exam on July 26th-this Friday- and I'm starting to freak out!!!

 

[Neil Shah]

as long as im not bored of XPC you can ask and when you are gonna appear fo the cies??

In the coming oct/november 2013 session... btw are u like gud at other subjects as well like eco?

 

[Neil Shah]

nah! I am just good in ICT and i opted for commerce not eco

haha

 

[Neil Shah]

Podar International School, Mumbai, and wbu?

 

[Neil Shah]

ahan great! I have finished my O Levels

no, as in which school r u frm

 

[Neil Shah]

* in which school u were?
anyway i did o levels from Lahore Grammar School, Lahore ! Have u given some of cie papers before?

nope ttyl