Physics: Post your doubts here!

[rz123]

Why not at right angles to the field? Imagine the proton traveling between the two parallel plates in the figure above this question. There will be a downward force on it and you calculate it from the electric field strength as F/Q so answer is charge on proton X 2.40 × 10–6 V m–1.

1st of all thanks 4 the response. ok if we take the figure on the previous question and imagine the proton to be coming initially bf4 entering the field at right angle to the field means coming straight nd the field is from positive to negative plate downward. now in the c part he asks us to calculate the acceleration of the proton at right angles to the field which i m not getting dat how it is zero. the proton will be coming like a mass in a projectile motion so it must have some acceleration at right angles to the field as well? :/ the marking scheme says its zero nd the force is at right angles to the field ? :|

 

[Doctor Nemo]

1st of all thanks 4 the response. ok if we take the figure on the previous question and imagine the proton to be coming initially bf4 entering the field at right angle to the field means coming straight nd the field is from positive to negative plate downward. now in the c part he asks us to calculate the acceleration of the proton at right angles to the field which i m not getting dat how it is zero. the proton will be coming like a mass in a projectile motion so it must have some acceleration at right angles to the field as well? :/ the marking scheme says its zero nd the force is at right angles to the field ? :|

I agree that makes no sense. Maybe the mark scheme is wrong.

 

[Doctor Nemo]

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_s11_qp_21.pdf

aslamoalikum...... wanted help in this paper question 5 part (b) ..??

Thank You

When the arrow of the potential divider is on the far left the 6 ohm resistor is in parallel with just the wire connecting the potential divider to the circuit. The voltage across this is 0 so the minimum current is 0.

When the arrow is on the far right the arrow is now in parallel with all the resistance of the variable resistor and in parallel with the battery. Now the full 12 volts is across the 6 ohm resistor and the maximum current is two amps.

 

[rz123]

I agree that makes no sense. Maybe the mark scheme is wrong.

yeah Dr Nemo i think the same. Thanks anyway.

 

[hm12]

can anybody explain nov 10 paper 43 question number 3

 

[Doctor Nemo]

yeah Dr Nemo i think the same. Thanks anyway.

Actually there are two right angles. Maybe they are referring to the right angle coming out of the paper so the situation is not like that of a magnetic field.

 

[Silent Hunter]

http://www.xtremepapers.com/CIE/ind...Level/9702 - Physics/&file=9702_w10_qp_12.pdf

Q 34 ...?

 

[rz123]

http://www.xtremepapers.com/CIE/index.php?dir=International A And AS Level/9702 - Physics/&file=9702_w10_qp_12.pdf

Q 34 ...?

i think it will be B because resistivity increases proportionally with the voltage. so graph will be least steep at first then more steep and then the steepest when the resistivity is 3p.

 

[unique840]

Help pls?

the question has the table of metals along with their work function energies. we hav 2 lights. one of wavelength 350 and one of 700. we will find the energies of both the lights and compare them with the work function energies. only potassium and light of 350 nm wavelength gives energy more than work function so it will give rise to photoelectric emission

 

[rz123]

worksheet 12, Q. 6 c part] (why is the ms saying dat current in lamp increases proportionally with resistance?)
R= V/I so current decreases with increase in resistance...:/

 

[DANGERBP]

worksheet 12, Q. 6 c part] (why is the ms saying dat current in lamp increases proportionally with resistance?)
R= V/I so current decreases with increase in resistance...:/

mm man is there by any chance ms would b wrong ?? coz if that was r8 ide kill myself =/ ! =@

 

[rz123]

mm man is there by any chance ms would b wrong ?? coz if that was r8 ide kill myself =/ ! =@

yo man remain easy! me not getting this 1. i guess the ms is faulty. ur life is much expensive then da filament lamp in the question causing the prob so chill man.

 

[DANGERBP]

yo man remain easy! me not getting this 1. i guess the ms is faulty. ur life is much expensive then a filament lamp so chill man.

hah okay good !
mm okay ide not think of suicidin for now u got a point lolol ;P

 

[MEGUSTA_xD]

yo man remain easy! me not getting this 1. i guess the ms is faulty. ur life is much expensive then da filament lamp in the question causing the prob so chill man.

Ms is wrong in some questions in this paper.

 

[Doctor Nemo]

When the arrow is towards the right, the the resistance of the variable resistance is 12 ohms, as it will provide resistance in the circuit. The two resistances are now in parallel, and the resistance is
1/12+1/6= 1/4.
So the reciprocal, gives us 4 ohms in the circuit, since I=V/R, shouldn't the it be 3 A? The maximum current? I know it's wrong, but I don't really get what you did.

And when the arrow is pointing towards the right, the resistance of the variable resistor is 0, so the resistance in the entire circuit is 6 ohms, and hence 2 A.

I know, I make no sense at all, but can you please elaborate what you did?

You are only interested in the current going through the 6 ohm resistor not the total current leaving the battery. The answer does not depend on the resistance of the variable resistor only the amount of the variable resistor that is in parallel with the 6 ohm resistor.

If the arrow was in the middle of the variable resistor then the 6 ohm resistor would be in parallel with 1/2 of the variable resistor. There is a 12 volt drop across the variable resistor and one half or 6 volts would also be across the 6 ohm resistor and there would be 1 amp through the 6 ohm resis

 

[Doctor Nemo]

why does capacitor store energy but not charge?

Good question

Because it has an equal number of plus and minus charges so the net charge in the capacitor is 0. A capacitor is like a rechargeable battery that can be quickly charged and decharged.

 

[hm12]

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w10_qp_43.pdf

please explain question number 3

 

[allysaleemally]

Hello,

which calculators can be used in AS Maths and Physics.
is this Casio one allowed http://edu.casio.com/products/standard/fx991es/
or do we have to use the basic one: http://edu.casio.com/products/standard/fx85ms/

some people say that u cant use the Fx 991 calculator(silver one)?

 

[usmiunique]

ASA,
i have many questions regarding paper 5. can anyoneplease tell me:
1) what is meant by error bars?
2) what is meant by worst acceptible line?
3) how do u calculate the error in the gradient?
4) how do u calculate the error the tabulated values which u have to calculate?
Also any notes on the apparatus and their use and how to write different kinds of experiments would be greatly appreciated!

 

[hassam]

http://www.xtremepapers.com/CIE/International A And AS Level/9702 - Physics/9702_w10_qp_43.pdf

please explain question number 3

can u be more specific please cos its a very long question.....i guess u ll be asking for that not in phase thing cos dats the difficult part in this.....so wat u need to do is to do a graph for original equation given prev. in question......and then shift it horizontal by 120 deg. in right direction.....one can ask why not in left direction ...thats because oscillation in that cylinder lead those of in prev by 120 deg....similarly do for 240 deg. phase shift....and then u cn see the displacemnt .....and thus draw positin of piston