Physics, Chemistry and Biology: Post your doubts here!

[Idrees_20020]

why does steel get permanently magnetized while iron doesn't?

Because steel is a hard magnetic material and iron is a soft magnetic material
Hard magnetic materials might be very difficult to magnetize but they retain their magnetism
Soft magnetic materials can be easily magnetized and demagnetized Usually soft magnetic materials dont retain magnetism for example iron will never be permanently magnetized

 

[Hanzalla]

Does anyone know how to use this formula and when to use it

Yes, In the book you can find it under the topic of Temperature/Thermometers
This is used when you have a thermometer in which only ice point and steam point are marked and you are given the length of the of the mercury expansion.

Temperature= (Length At Unknown temperature - Length at Ice Point)/(Length at Steam point - Length at Ice Point) x100

Hope my explanation is good enough xD

no idea

No Clue about it

 

[ziiiii]

Would appreciate if someone could help out on this physics question (2016 Oct/Nov paper 42, Question 2 b ii.) - with explanations.

Here is the examiner report:
"The correct answer was only given by stronger candidates with the answer 900N being the most popular."
Where the correct answer was 100N... but Why!?

 

[Hanzalla]

Would appreciate if someone could help out on this physics question (2016 Oct/Nov paper 42, Question 2 b ii.) - with explanations.

Here is the examiner report:
"The correct answer was only given by stronger candidates with the answer 900N being the most popular."
Where the correct answer was 100N... but Why!?

Over here he asks the RESULTANT FORCE on the OBJECT soo
As 500N downward force and 400N upward force therefore resultant will be 500N-400N= 100N Downward force

 

[ziiiii]

Over here he asks the RESULTANT FORCE on the OBJECT soo
As 500N downward force and 400N upward force therefore resultant will be 500N-400N= 100N Downward force

Thank you very much for your reply, explanations were clear as well!
But... Why CAN'T "resultant force" be calculated in terms of Clockwise/Anticlockwise? Why does it have to be Upward/Downward?

 

[Hanzalla]

Thank you very much for your reply, explanations were clear as well!
But... Why CAN'T "resultant force" be calculated in terms of Clockwise/Anticlockwise? Why does it have to be Upward/Downward?

The Clockwise/AntiClockwise you're referring to are MOMENTS, He has already asked for resultant moment in the previous part. When he asks for force, you may forget that theres a pivot and the object can rotate etc etc. You have to remember that since these FORCES are opposite in direction, you will have to subtract them to calculate the resultant. Just like any other object be it a cube or ball. Hope you get the point

 

[ziiiii]

The Clockwise/AntiClockwise you're referring to are MOMENTS, He has already asked for resultant moment in the previous part. When he asks for force, you may forget that theres a pivot and the object can rotate etc etc. You have to remember that since these FORCES are opposite in direction, you will have to subtract them to calculate the resultant. Just like any other object be it a cube or ball. Hope you get the point

Thank you very much! I understand it now!!
Thanks for helping me!

 

[Adeen Atif]

Yes, In the book you can find it under the topic of Temperature/Thermometers
This is used when you have a thermometer in which only ice point and steam point are marked and you are given the length of the of the mercury expansion.

Temperature= (Length At Unknown temperature - Length at Ice Point)/(Length at Steam point - Length at Ice Point) x100

Hope my explanation is good enough xD

Its in yellow portion,so Its not in out syllabus.Btw is it related to absolute zero or something?

 

[Adeen Atif]

yup, they can ask us to draw the ray box

Oh,Cause its not in my book!

 

[Adeen Atif]

Btw guys in Znotes,its written that "The current is maximum when the coil is horizontal,since magnetic fields are being cut at the fastest rate and 0 when the coil is vertical,since its cutting NO field lines"
So how is it correct,Because as far as I know the magnetic field lines are horizontal ,so more magnetic field lines should be cut when the coil is vertical.
+Ive confirmed this statement from another website and even they are saying the same thing as the notes

 

[Ayesha Asif333]

Because steel is a hard magnetic material and iron is a soft magnetic material
Hard magnetic materials might be very difficult to magnetize but they retain their magnetism
Soft magnetic materials can be easily magnetized and demagnetized Usually soft magnetic materials dont retain magnetism for example iron will never be permanently magnetized

Yes, In the book you can find it under the topic of Temperature/Thermometers
This is used when you have a thermometer in which only ice point and steam point are marked and you are given the length of the of the mercury expansion.

Temperature= (Length At Unknown temperature - Length at Ice Point)/(Length at Steam point - Length at Ice Point) x100

Hope my explanation is good enough xD

Thanks vm

 

[Ayesha Asif333]

Oh,Cause its not in my book!

Not a problem, they usually ask to draw a ray box in p6
have u seen a ray box for real and done reflection, refraction, dispersion experiments ?

 

[Ayesha Asif333]

Btw guys in Znotes,its written that "The current is maximum when the coil is horizontal,since magnetic fields are being cut at the fastest rate and 0 when the coil is vertical,since its not cutting NO field lines"
So how is it correct,Because as far as I know the magnetic field lines are horizontal ,so more magnetic field lines should be cut when the coil is vertical.
+Ive confirmed this statement from another website and even they are saying the same thing as the notes

For the current to be induced in the conductor/wire the magnetic field lines should cut the conductor, that means the conductor should be perpendicular to the field lines in any orientation , this will be the case when the straight wire lies horizontally between the U shaped magnet
Does it make sense?

 

[Khadu33]

guys need ur help >why would a brass key not sink if its attached on a wood?

 

[Aayan Muttaqi]

Guys, question from physics CIE 0625/31/O/N/2008 , 5(c)(i)
Using a 40W heater, 16.3 g of ice is melted in 2.0 minutes. The heater is then switched off. In a further 2.0 minutes, 2.1 g of ice is melted.
Calculate the value of the specific latent heat of fusion of ice from these results.

 

[Hanzalla]

guys need ur help >why would a brass key not sink if its attached on a wood?

Because The wood is less dense then water and will float obviously?

 

[Adeen Atif]

Not a problem, they usually ask to draw a ray box in p6
have u seen a ray box for real and done reflection, refraction, dispersion experiments ?

Ive done the refraction,reflection and diversion experiments,But ive never seen a ray box.
So that means it doesn't come in Paper 4??

 

[Adeen Atif]

For the current to be induced in the conductor/wire the magnetic field lines should cut the conductor, that means the conductor should be perpendicular to the field lines in any orientation , this will be the case when the straight wire lies horizontally between the U shaped magnet
Does it make sense?

Sorry?
But if the coil is horizontal ,so the magnetic field lines are also horizontal,Then how are they cut then?

 

[Khadu33]

Guys, question from physics CIE 0625/31/O/N/2008 , 5(c)(i)
Using a 40W heater, 16.3 g of ice is melted in 2.0 minutes. The heater is then switched off. In a further 2.0 minutes, 2.1 g of ice is melted.
Calculate the value of the specific latent heat of fusion of ice from these results.

40W x 2min will gv energy then less the masses and apply the formular L=ENERGY divide by mass

 

[Hanzalla]

Sorry?
But if the coil is horizontal ,so the magnetic field lines are also horizontal,Then how are they cut then?

Its like when a tyre is pushed down a cliff, when it reaches the bottom of the cliff, It will have the greatest Kinetic Energy even though there is no steep road ahead of it . Same goes for the coil. You can assume that tyre on the bottom of the cliff is Coil at horizontal position. OMG I cant convey what I want to make you understand xD