Physics: Post your doubts here!

[princess Anu]

Explain why the alternating current in the primary coil of a transformer is not in phase with the alternating e.m.f. induced in the secondary coil.

Because the current in the primary coil is in phase with the flux in the core
But not the change in the flux, (change in the flux is not in phase with the flux in the core) ,and it is the change in flux that generates the alternating emf hence we say Alternating Current is not in phase with the Alternating emf

 

[princess Anu]

Yeah but what if it were
What could have been the possible side...:/

View attachment 60187
Chill

 

[princess Anu]

I can't visualise this question
Which part of the needle is oscillating and how is it oscillating( which direction)? why is the amplitude 11mm? + in bi needle should be at its max height, i get it , but why is this max height 14mm below cloth or 8mm above cloth?
Can someone draw on the figure and explain
Please



bi

 

[The Sarcastic Retard]

Yeah but what if it were
What could have been the possible side...:/

There is a mistake in that part of question. So we are confused.

 

[The Sarcastic Retard]

Because the current in the primary coil is in phase with the flux in the core <-------- How do we know this??
But not the change in the flux. <-------- change is flux wont be generated as we using ac?

So why does change in the flux not in hase with flux in the core.

 

[The Sarcastic Retard]

I can't visualise this question
Which part of the needle is oscillating and how is it oscillating( which direction)? why is the amplitude 11mm? + in bi needle should be at its max height, i get it , but why is this max height 14mm below cloth or 8mm above cloth?
Can someone draw on the figure and explain
Please



biView attachment 60196

No one solved my this doubt. I had the same doubt a month ago.

 

[areeba240]

helpppp plzzzzzzzzzzzzzz
thanks in advance

 

[areeba240]

helppppp plzzzzzzzz
thanks in advance

 

[farhan141]

Because the current in the primary coil is in phase with the flux in the core <-------- How do we know this??
But not the change in the flux. <-------- change is flux wont be generated as we using ac?

So why does change in the flux not in hase with flux in the core.

Im also confused with this bs. I have not studied it anywhere that this happens but in marking scheme they have explained as if we know it.

 

[The Sarcastic Retard]

Explain why the alternating current in the primary coil of a transformer is not in phase with the alternating e.m.f. induced in the secondary coil.

Physicist

 

[The Sarcastic Retard]

 

[The Sarcastic Retard]

@

I can't visualise this question
Which part of the needle is oscillating and how is it oscillating( which direction)? why is the amplitude 11mm? + in bi needle should be at its max height, i get it , but why is this max height 14mm below cloth or 8mm above cloth?
Can someone draw on the figure and explain
Please



biView attachment 60196

Physicist

 

[The Sarcastic Retard]

tell me from which year and paper this is. i remember explaining this.
or give me the question itself

http://papers.gceguide.com/A Levels/Physics (9702)/9702_s15_qp_42.pdf
7b) found

 

[The Sarcastic Retard]

see 1033 at
http://physics-ref.blogspot.com/2015/10/physics-9702-doubts-help-page-216.html

I dont understand that lines u have written.

 

[farhan141]

see 1033 at
http://physics-ref.blogspot.com/2015/10/physics-9702-doubts-help-page-216.html

I got the primary coil thing but not the link/cut/thread secondary coil part

 

[nadeen64]

Can someone please explain this question? Answer is D

 

[Rizwan Javed]

Can someone please explain this question? Answer is D

View attachment 60213

When two objects have an elastic collision, the relative speed of approach is equal to the relative speed of separation.
When two objects are moving towards each others, the relative speed of one object relative to the other is given by sum of the speeds of two objects. So relative speed of appraoch here is u1 + u2.

When two objects are moving in a same direction, then the relative speed of an object is calculated by subtracting the individual speeds of the two objects. So the relative speed of separation here is given by: v2-v1

As stated above: "When two objects have an elastic collision, the relative speed of approach is equal to the relative speed of separation. ", the equation for this situation will become:

u1 + u2 = v2 - v1

So answer is D.

 

[Saad the Paki]

When two objects have an elastic collision, the relative speed of approach is equal to the relative speed of separation.
When two objects are moving towards each others, the relative speed of one object relative to the other is given by sum of the speeds of two objects. So relative speed of appraoch here is u1 + u2.

When two objects are moving in a same direction, then the relative speed of an object is calculated by subtracting the individual speeds of the two objects. So the relative speed of separation here is given by: v2-v1

As stated above: "When two objects have an elastic collision, the relative speed of approach is equal to the relative speed of separation. ", the equation for this situation will become:

u1 + u2 = v2 - v1

So answer is D.

Is this method valid only when the masses of the 2 objects are equal or whenever there is an elastic collision?

 

[nadeen64]

When two objects have an elastic collision, the relative speed of approach is equal to the relative speed of separation.
When two objects are moving towards each others, the relative speed of one object relative to the other is given by sum of the speeds of two objects. So relative speed of appraoch here is u1 + u2.

When two objects are moving in a same direction, then the relative speed of an object is calculated by subtracting the individual speeds of the two objects. So the relative speed of separation here is given by: v2-v1

As stated above: "When two objects have an elastic collision, the relative speed of approach is equal to the relative speed of separation. ", the equation for this situation will become:

u1 + u2 = v2 - v1

So answer is D.

Im still confused. When the objects are approaching, they are in different directions and when they're separating, they go in the same direction. so why not A?

 

[Rizwan Javed]

Is this method valid only when the masses of the 2 objects are equal or whenever there is an elastic collision?

It is applicable whenever objects have an elastic collision.