Physics: Post your doubts here!

[Galactic]

Other materials dont have the proper alignment of north and south pole and the materials whose alignment cant be changed by the magnet are not attracted by the magnet.

What exactly do you mean by "proper alignment" ? And why don't they have proper alignment? And why can a magnet change the alignment of iron but not of for example wood or paper?

 

[Hassan Ali Abid]

What exactly do you mean by "proper alignment" ? And why don't they have proper alignment? And why can a magnet change the alignment of iron but not of for example wood or paper?

thats what i meant with alignment ....when the magnetic substances are gets their proper alignment having proper direction of north and south pole then they are magnetized and thats the reason why they are attracted to the magnets..

 

[Nawal Mahmood]

Assalamualikum wr wb!
I'm stuck in this question and I was wondering if anyone could help me out a little bit.
Q: Monochromatic radiation of wavelength 546nm falls of a potassium surface of area 7.5cm ^2 in an evacuated chamber. intensity of surfave is 60Wm^2 and it may be assumed that 1% of the photons wmit electrons from the surface. what is the photoelectric current?
What I did is , found the intensity=power/area. power=energy/time. So, I found time this way and applied this time in the formula of , current=charge /time. I multilpied the charge with 19 bcuz that's the atomic no. of potassium.
I'm not getting the right answer which is 0.020 micro Amps. What am I doing wrong? Help?

 

[Nawal Mahmood]

Assalamualikum wr wb!
I'm stuck in this question and I was wondering if anyone could help me out a little bit.
Q: Monochromatic radiation of wavelength 546nm falls of a potassium surface of area 7.5cm ^2 in an evacuated chamber. intensity of surfave is 60Wm^2 and it may be assumed that 1% of the photons wmit electrons from the surface. what is the photoelectric current?
What I did is , found the intensity=power/area. power=energy/time. So, I found time this way and applied this time in the formula of , current=charge /time. I multilpied the charge with 19 bcuz that's the atomic no. of potassium.
I'm not getting the right answer which is 0.020 micro Amps. What am I doing wrong? Help?

 

[TheStallion-Reborn]

In AS physics, my teacher made me study projectile motion, but I cannot find it in the syllabus. Can anyone please clarify?

 

[sara kamal]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s11_qp_41.pdf

please explain Q9 and Q10c(2)

 

[ShreeyaBeatz]

PLEASE HELP! HOW DO YOU CALCULATE THIS ?? I COULDNT REACH THE ANSWER
A student wishes to determine the density ρ of lead. She measures the mass and diameter of a
small sphere of lead:
mass = (0.506 ± 0.005) g
diameter = (2.20 ± 0.02) mm.
What is the best estimate of the percentage uncertainty in her value of ρ ?
A 1.9% B 2.0% C 2.8% D 3.7%

 

[ShreeyaBeatz]

Other materials dont have the proper alignment of north and south pole and the materials whose alignment cant be changed by the magnet are not attracted by the magnet.

please answer my question Hassan ! thread no #6472

 

[goodluckayesha]

can any1 explain hall probe thing

 

[Hassan Ali Abid]

please answer my question Hassan ! thread no #6472

View attachment 35486

Just check it out if the Ans is D or not ....but the procedure is this to solve uncertainty questions.

 

[Hassan Ali Abid]

can any1 explain hall probe thing

Hall probe is used to to measure Magnetic flux density and for this it uses hall effect.

F(magnetic) = eE

F(magnetic)=F(electric)
qvB=eE

E=V(Hall) / d

so qvB=eE becomes
qvB=e.V(Hall) / d

Hall voltage =vBd.
...........................................

hall probe is made of semi conductor material and two wires are connected to both ends of the semiconductor which is supplying a constant currect I. there are two more wires connected to the opposite edges of semiconductor and a volt meter is also connected to the terminals to measure Hall p.d.

as Hall voltage =vBd
V(hall) directly proportional to B

Then hall probe is placed in magnetic felid whose flux density (B) is unknown and then corresponding HAll p.d V is noted

B= (Voltage/unknown voltage) .B not

 

[goodluckayesha]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s10_qp_53.pdf
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w10_qp_51.pdf
http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_w10_qp_53.pdf
thnx a bunch..... if possible plz post the daigrams or the above pprs the first questions.... in the first link the question says to use a hall probe along with the the daigram can u give a brief explanation and for the other links too it wud be v.helpful for me thnx in advance...May Allah bless u...

Hall probe is used to to measure Magnetic flux density and for this it uses hall effect.

F(magnetic) = eE

F(magnetic)=F(electric)
qvB=eE

E=V(Hall) / d

so qvB=eE becomes
qvB=e.V(Hall) / d

Hall voltage =vBd.
...........................................

hall probe is made of semi conductor material and two wires are connected to both ends of the semiconductor which is supplying a constant currect I. there are two more wires connected to the opposite edges of semiconductor and a volt meter is also connected to the terminals to measure Hall p.d.

as Hall voltage =vBd
V(hall) directly proportional to B

Then hall probe is placed in magnetic felid whose flux density (B) is unknown and then corresponding HAll p.d V is noted

B= (Voltage/unknown voltage) .B not

 

[goodluckayesha]

http://papers.xtremepapers.com/CIE/...nd AS Level/Physics (9702)/9702_s10_qp_41.pdf
in this can u explain the 5a plzzzzzzz

 

[Hassan Ali Abid]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_41.pdf
in this can u explain the 5a plzzzzzzz

when it is rotated the angle b/w B and probe is varying and cz of this the Hall p.d is changing from max +ve --> max -ve ....just see that when magnetic felid is at 90 degree to the probe the V(hall) gets max +Ve ...
Did u get or you are still confused with it ?

 

[goodluckayesha]

when it is rotated the angle b/w B and probe is varying and cz of this the Hall p.d is changing from max +ve --> max -ve ....just see that when magnetic felid is at 90 degree to the probe the V(hall) gets max +Ve ...
Did u get or you are still confused with it ?

n when is it max -ve? somewht im starting to get the concept
actually this topic im doing self study no help so its tough fo me to get sorry

 

[Hassan Ali Abid]

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_s10_qp_53.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_51.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w10_qp_53.pdf
thnx a bunch..... if possible plz post the daigrams or the above pprs the first questions.... in the first link the question says to use a hall probe along with the the daigram can u give a brief explanation and for the other links too it wud be v.helpful for me thnx in advance...May Allah bless u...

For 's10_qp_53.pdf'
u have to draw a hall probe .....first make a 3.D rectangle and from one side u have to attach the voltmeter to measure hall voltage ...from one side the wires are attached having the current I ...and the third side is used to oass the magnetic feild lines .....*u have to explain about its calibration too*
make sure that u draw in such a way that B is having a 90 degree angle to probe.....

P.s for attempting these questions u have to study Hall effect + hall probe and its calibration in detail otherwise its too difficult to solve these questions.

 

[Hassan Ali Abid]

n when is it max -ve? somewht im starting to get the concept
actually this topic im doing self study no help so its tough fo me to get sorry

max -ve when it is at 180 angle .. ...
but Let me confirm it first then i'll explain this max-ve thing .

 

[goodluckayesha]

For 's10_qp_53.pdf'
u have to draw a hall probe .....first make a 3.D rectangle and from one side u have to attach the voltmeter to measure hall voltage ...from one side the wires are attached having the current I ...and the third side is used to oass the magnetic feild lines .....*u have to explain about its calibration too*
make sure that u draw in such a way that B is having a 90 degree angle to probe.....

P.s for attempting these questions u have to study Hall effect + hall probe and its calibration in detail otherwise its too difficult to solve these questions.

what abt the calibeation?oh god this is hard

 

[goodluckayesha]

max -ve when it is at 180 angle .. ...
but Let me confirm it first then i'll explain this max-ve thing .

okss

 

[Hassan Ali Abid]

what abt the calibeation?oh god this is hard

If its not calibrated then how can u measure the unknown B..

i have already stated that B=(voltage/Voltage (not) ) .B (not)

when Voltage (not) and B (not) is calculated then only we can measure unknown B.