Physics: Post your doubts here!

[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

 

[biscuitbiscuit]

Someone please explain Q7 b (i) and (ii), link:

http://papers.xtremepapers.com/CIE/...and AS Level/Physics (9702)/9702_w08_qp_2.pdf

 

[♫Prince Shah♫]

Someone please explain Q7 b (i) and (ii), link:

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w08_qp_2.pdf

bi)As temperature increases, Resistance of a thermistor decreases ...so, talking abut Potential diff of 2kohm voltage reading increases so u can also say that pd across 5kohm.. thermistor resistance decreases..!!!
bii) i am not sure

 

[boredome]

Can u

(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.

Can u please write the equation or explain how Current is directly proportional to magnetic flux?

 

[!!..Purple Ghost..!!]

Can u


Can u please write the equation or explain how Current is directly proportional to magnetic flux?

The amount of current in a coil directly relates to magnetic field strength
Moving charges create magnetic fields. Each electron moving in a conductor creates its own magnetic field. As electrons move through the coil of wire, the magnetic field of one electron adds to the field of any others moving in the same direction. The faster a charge moves, the stronger the magnetic field it creates. For this reason alone, a higher current implies an electron is moving faster, and as a result, it would create a stronger magnetic field.

 

[BreakingBad]

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

Stress is force per unit area. The area is a hundred times smaller so A probably. Besides, options B,C and D are absurd. It would make more sense if those numbers were more like 1000 times, 10 times etc.

Someone please explain Q7 b (i) and (ii), link:

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Physics (9702)/9702_w08_qp_2.pdf

i) Already been answered.
ii)
P.d. across the thermistor and the 5000 ohms resistor combined is 6-3.6 = 2.4V
The current in the circuit is V/R = 3.6/2000 = 0.0018A

Therefore, combined resistance for the thermistor and the 5000 ohms resistor is V/I = 2.4/0.0018 = 1333.333 ohms

1/RT = 1/Rt + 1/Rr
1/1333.333 = 1/Rt + 1/5000
Rt = 1820 ohms
Sorry but I haven't been looking at most of the convos lately.

 

[!!..Purple Ghost..!!]

h3lp me in electronics part.. i cant understand it at all As level..