Physics: Post your doubts here!

[goodluckayesha]

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.

do we need to know hw to caliberate ? n hw do we do tht

 

[Hassan Ali Abid]

do we need to know hw to caliberate ? n hw do we do tht

I guess yes we need to know about that ...
placing the hall probe in known B and then calculating the hall p.d then placing the values in above formula when the probe is in unknown magnetic feild ..

 

[Galactic]

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..
View attachment 35048

Why aren't other substances aligned? What's so special about ferromagnetic materials that they are the only ones aligned due to a magnet? Also what exactly in iron is aligned?? The atoms or electrons???

 

[Autumngirl]

I have a doubt about wires in a single cable.
If you go through the examiner report for ON2007 P2 Q6, it states that the two copper wires were to be taken in series not parallel. But then for Q32 in ON 2008 P1 the examiner report for that exam says that the wires were to be taken in parallel not series.
Both the cables look the same to me so why the different solutions?

 

[Galactic]

A circuit has 3 branches. Two of the branches have resistors but one is empty. Will the current in the empty branch be the full current due to the battery OR will it be the divided current ? And if it's divided, how will it be? Keep in mind, the branch has no resistor or device.

 

[Saad Mughal]

HOW TO SOLVE THIS

screen capture windows

Solution:
Assuming the table to be a smooth surface (frictionless).
Loss in Gravitational Potential Energy = Gain in Kinetic Energy
Loss in G.P.E. = K.E. of mass + K.E. of trolley
0.5*9.8*1 = 0.5(0.5)(v)^2 + 0.5(1.5)(v)^2
0.25v^2 + 0.75v^2 = 4.9
v^2 = 4.9

Considering trolley,
K.E. = 0.5(1.5)(4.9) = 3.675 ~ 3.7 J

 

[Hassan Ali Abid]

A circuit has 3 branches. Two of the branches have resistors but one is empty. Will the current in the empty branch be the full current due to the battery OR will it be the divided current ? And if it's divided, how will it be? Keep in mind, the branch has no resistor or device.

The current will not divide and the current will flow from the path which is having the least resistance or hindrance thats why the whole current will flow from the branch which is empty as long as battery is having negligible internal resistance.

 

[talha-_-khan]

how to do a screenshot on a pc

 

[Galactic]

The current will not divide and the current will flow from the path which is having the least resistance or hindrance thats why the whole current will flow from the branch which is empty as long as battery is having negligible internal resistance.

Thanks a lot!! That cleared my problem Jazakallah

 

[BreakingBad]

Why aren't other substances aligned? What's so special about ferromagnetic materials that they are the only ones aligned due to a magnet? Also what exactly in iron is aligned?? The atoms or electrons???

Many materials have unpaired electron spins, and the majority of these materials are paramagnetic. When the spins interact with each other in such a way that the spins align spontaneously, the materials are called ferromagnetic (what is often loosely termed as magnetic). Because of the way their regular crystalline atomic structure causes their spins to interact, some metals are ferromagnetic when found in their natural states. These include iron, cobalt, nickel etc.

how to do a screenshot on a pc

Can you clarify what is option D? It might be easier to explain knowing the answer.

 

[BreakingBad]

I have a doubt about wires in a single cable.
If you go through the examiner report for ON2007 P2 Q6, it states that the two copper wires were to be taken in series not parallel. But then for Q32 in ON 2008 P1 the examiner report for that exam says that the wires were to be taken in parallel not series.
Both the cables look the same to me so why the different solutions?

I didn't take a look at the examiner report but when i solved the questions, both the cases require the wires to be in parallel. The wires in the cables are always parallel. ON2008 also requires you to take the wires in parallel otherwise you wouldn't be able to get B as your answer.

 

[Galactic]

Many materials have unpaired electron spins, and the majority of these materials are paramagnetic. When the spins interact with each other in such a way that the spins align spontaneously, the materials are called ferromagnetic (what is often loosely termed as magnetic). Because of the way their regular crystalline atomic structure causes their spins to interact, some metals are ferromagnetic when found in their natural states. These include iron, cobalt, nickel etc.



Can you clarify what is option D? It might be easier to explain knowing the answer.

Okay! Got that, thanks!!

 

[talha-_-khan]

Many materials have unpaired electron spins, and the majority of these materials are paramagnetic. When the spins interact with each other in such a way that the spins align spontaneously, the materials are called ferromagnetic (what is often loosely termed as magnetic). Because of the way their regular crystalline atomic structure causes their spins to interact, some metals are ferromagnetic when found in their natural states. These include iron, cobalt, nickel etc.



Can you clarify what is option D? It might be easier to explain knowing the answer.

answer is B:59J

 

[talha-_-khan]

how o do a screenshot on a pc

HOW TO SOLVE

Loss in gpe of Y = Gain in gpe of X + Gain in Kinetic Energy of X and Y
( 5 x 9.8 x 2 ) = ( 4 x 9.8 x 1 ) + ( 0.5 x 9 x v^2 )
98 = 39.2 + 4.5 v^2
v = 3.6

total KE of SYSTEM = 0.5 x 9 x 3.6^2 = 58

 

[talha-_-khan]

HOW TO SOLVE THIS

download screenshot

 

[Asad rehman]

Re: Physics Help here! Stuck somewhere?? Ask here!

i need help for june 2007 paper2 q5b

 

[Hassan Ali Abid]

i need help for june 2007 paper2 q5b

Stationary wave is produced inside the tube ...it means it has nodes and antinodes...and max displacement is at antinodes and min at nodes so dust heaps are formed on nodes (as the displacement at nodes is zero).

 

[boredome]

I need help with paper 4 june 05 Q6 .. thnx in advance

 

[Hassan Ali Abid]

I need help with paper 4 june 05 Q6 .. thnx in advance

(a) 1. Alternating current will produce an magnetic field(Flux) in the core so due to this there wil be change in flux in secondary coil and then emf will be induced in the secondary coil.

2. the power is contant ..ie the input power given should be equal to the output power so if V is increased the I will be decreased to reduce the power losses.

(b)1.current I is directly proportional to Flux so the graph will have same shape as of the above graph shown in the question .
2. the shape of this graph will be of cosine graph ... when flux is zero emf is max and when flux max then the emf is 0.

 

[shaheerrn]

A model is made of the crane, its load and the cable supporting the load.
The material used for each part of the model is the same as that in the full-size crane, cable and
load. The model is one tenth full-size in all linear dimensions.
What is the ratio
stress in the cable on the model crane
stress in the cable on the full s ize crane
- ?
A 100 B 101 C 102 D 103