A2 Physics | Post your doubts here

[angelicsuccubus]

so what's gonna help me more.. doing all the past papers, or reading the entire text book considering I only have 28 hours left before my exam?

 

[OrlandoBloom<3]

Sorry for the late reply!
This is a really big question. Like, there are two hand rules.
The left hand rule is to predict the direction of a force on a current carrying conductor in a magnetic field. In this one, when the conductor carrying a current is placed in a uniform magnetic field, a field is also created from the current carrying wire, and so, there is a resultant force on the wire.

The right hand rule is to predict the direction of induced emfs and currents in a straight conductor. So, this is the one where the conductor is cutting the flux in the conductor, and a emf is generated. It is where the formula E= -d(flux) / dt is used and proves Faraday's Law.

Sorry for the IGCSE type explanation, but the question is very general.

Thanks alot I know its general I just get really confused all the time |!|

 

[ABDSyed]

the needle oscillate through a total distance of 22cm...means at equalibrium it will be at 22/2=11cm

Thanks A lot

 

[angelgirl:)]

so what's gonna help me more.. doing all the past papers, or reading the entire text book considering I only have 28 hours left before my exam?

better to solve the past paer now i guess ...thats wat iam doin right now...coz u will be more confednt for solving the questions...

 

[ABDSyed]

in the first line the question says that the needle travels a total distance of 22mm . amplitude is half the distance traveled in one cycle . = 22/2 = 11mm

Thanks Bro

 

[Jonathan127]

so what's gonna help me more.. doing all the past papers, or reading the entire text book considering I only have 28 hours left before my exam?

Um, If i were you, I'd read the text book. Past papers help but you'll feel more confident if you read the text book BUT you have to understand the text book and the concepts otherwise its useless. I remember for AS level. I only did 5 past papers, but I really read my notes carefully and I got an A.

 

[angelicsuccubus]

Sorry for the late reply!
This is a really big question. Like, there are two hand rules.
The left hand rule is to predict the direction of a force on a current carrying conductor in a magnetic field. In this one, when the conductor carrying a current is placed in a uniform magnetic field, a field is also created from the current carrying wire, and so, there is a resultant force on the wire.

The right hand rule is to predict the direction of induced emfs and currents in a straight conductor. So, this is the one where the conductor is cutting the flux in the conductor, and a emf is generated. It is where the formula E= -d(flux) / dt is used and proves Faraday's Law.

Sorry for the IGCSE type explanation, but the question is very general.

you people make it so much to remember.. the only difference, literally is that the right hand rule is when protons are travelling, and the left when electrons are flowing. Everything else is just force and field.

 

[leadingguy]

ho i did is....SQrsinwt...from the aii answer..
which can be written as x=x.sinwt....
v=dx/dt=x.wcoswt
a=-xw^2
a is proportional to -x...means S.H.M....by differentiation...i guess i copied from the ms...i didnt remember...
a=d^2x/dt^2 = -x.w^2sinwt.....

sorry bt I am unable to understand a single word write clearly and ask what are u confused at????

I just differentiated the R (eq. fr finding amplitude) creating an eq, fr V (velocity ) and then again differentiated it to get amplitude . then put the values of theta in it to get the ans

Wow, such a complicated answer but its the only one that makes sense so far. I'm sure there is a more simple answer since its only 2 marks. I did that paper a few days ago, and then gave up on it and hoped it wouldn't be in the exam .

in paper there is no need to show the whole procedure jxt state that

r = r.sinwt

a = - r.w^2.sinwt

acceleration max. so sin90 and therefore a = - r.w^2 proven

 

[angelicsuccubus]

Um, If i were you, I'd read the text book. Past papers help but you'll feel more confident if you read the text book BUT you have to understand the text book and the concepts otherwise its useless. I remember for AS level. I only did 5 past papers, but I really read my notes carefully and I got an A.

ack... this is gonna be a long 28 hour period..

 

[Jonathan127]

sorry bt I am unable to understand a single word write clearly and ask what are u confused at????

I just differentiated the R (eq. fr finding amplitude) creating an eq, fr V (velocity ) and then again differentiated it to get amplitude . then put the values of theta in it to get the ans




in paper there is no need to show the whole procedure jxt state that

r = r.sinwt

a = - r.w^2.sinwt

acceleration max. so sin90 and therefore a = - r.w^2 proven

Ok, thanks for the answer . I don't know how I'll have time to figure out questions like that, cause I always find the time too little.

 

[Jonathan127]

you people make it so much to remember.. the only difference, literally is that the right hand rule is when protons are travelling, and the left when electrons are flowing. Everything else is just force and field.

Which protons?? Now you've confused me!

 

[Mobeen]

Which protons?? Now you've confused me!

i guess she was just talking about the rules in general not any question ..

 

[angelgirl:)]

i guess she was just talking about the rules in general not any question ..

but frm where proton came in these rules?

 

[angelicsuccubus]

hey.. did you guys see any question with a circuit using a photocell in it?

 

[angelgirl:)]

hey.. did you guys see any question with a circuit using a photocell in it?

noooo!

 

[angelicsuccubus]

Which protons?? Now you've confused me!

oh I'm sorry... umm it's because the second finger gives the direction of conventional current, so from positive to negative .. that's actually the flow of protons (sorry my physics comes from everywhere else but the A level syllabus)

Just ignore me.. it was something I noticed while doing questions that used these rules a long time ago.. so I must be mixing something up.

 

[Mobeen]

but frm where proton came in these rules?

the left hand rule has got protons doesnt it ? the second finger shows the direction of the protons , alpha nucleus or whatever given

 

[angelicsuccubus]

noooo!

kk, good

 

[Jonathan127]

the left hand rule has got protons doesnt it ? the second finger shows the direction of the protons , alpha nucleus or whatever given

No, the thumb shows the direction of the movement, the first finger/ index finger shows the direction of the field, and the the second finger shows the direction of the induced current/ EMF.

 

[angelicsuccubus]

the left hand rule has got protons doesnt it ? the second finger shows the direction of the protons , alpha nucleus or whatever given

thank god! I thought I was making physics up! ... do we need to know anthing about the stopping potential?