Biology; Chemistry; Physics: Post your doubts here!

[snowbrood]

just wanna quick confirmation:

When switch is open, current is 1.
When switch is closed, current is 1.8,

and that in the question they have rounded off 1.8 to 2.

how did u get the answer 1.8 can u explain

 

[snowbrood]

its s03 p2 q11 (c) The ship moves to a place where the sea is deeper.
(i) State and explain two changes that would occur to the reflected pulses on the c.r.o.
trace. You may give diagrams of the old and new traces to show the changes.
(ii) When the sea is more than 450m deep, the ultrasound pulses must be sent out less
often. Using data from Fig. 11.2, explain why this is necessary.
[6] can u solve guys

 

[SalmanPakRocks]

when the switch is open then the reading is 1A but when the switch is closed then the reading is
since the switch is closed so the following becomes the paralled circuit so current divides, thus at first resistor the current is 2A but then the current divides up into 1A and 1A so the total current = 1+1=2. I don't know if i applied the correct theory or not.

 

[snowbrood]

i gues the current wont flow in the other resistor once the circuit is closed

 

[SalmanPakRocks]

i gues the current wont flow in the other resistor once the circuit is closed

why not? Current will flow through both the resistors in each cases.

 

[ailg1996]

What is short circuiting?

 

[Silent Hunter]

A short circuit in an electrical circuit allows a current to travel along an unintended path

 

[Anon]

What is short circuiting?

When there are more components on a single outlet, more current flows through the wire. Therefore wire heats up.
The hot wire causes insulation around it to melt, and which ultimately causes the negative and positive terminals to come in contact. As both the terminals are in contact, and their is minimal resistance, it causes huge amount of current to flow which would cause fire and explosion...

how did u get the answer 1.8 can u explain

I calculated as 1.8 because;


In paralell circuit, total resistance is:

1 = 1 + 1 ... 1
R . R1.. R2.. Rn

This is a paralell series circuit when switch is closed,

One resistor is in series with battery,
The other resistor is in paralell.

As there is only one branch, we will take resistance in the branch as "1/3" (resistor is 3 ohms, we apply, 1/R thingy)

The other which is in series, so it would simply be added..

so it is : 3 + 1/3 = 10/3 Ans

Suppose has there been another branch of 3 ohms resistor, it would then be:

3 + 1/3 + 1/3 = whatev



I still think something is wrong with this ques tho...

 

[snowbrood]

brother current dont flows in the rest of the circuit once the switch is on.... i have done a practical right now and this is what i get 2Amps and no current flowing in the end resistor

 

[scouserlfc]

its s03 p2 q11 (c) The ship moves to a place where the sea is deeper.
(i) State and explain two changes that would occur to the reflected pulses on the c.r.o.
trace. You may give diagrams of the old and new traces to show the changes.
(ii) When the sea is more than 450m deep, the ultrasound pulses must be sent out less
often. Using data from Fig. 11.2, explain why this is necessary.
[6] can u solve guys

although have done CRO but not sound and waves i might be wrong but ill try !
in the first part one change will be time increases as the distance has increased and the speed of ultrasound wave remains same so time increases than before and one more thing always in water i remember this that the some waves are lost to water,rocks in deep the further it goes so the reflected ray would be small in amplitude !

and the second part i think that u can now understand from the earlier parts last answer why it shud not be sent often as more time taken so u have to wait for a reflected ray before sending another ray or else u may have problems !

 

[Anon]

brother current dont flows in the rest of the circuit once the switch is on.... i have done a practical right now and this is what i get 2Amps and no current flowing in the end resistor

When I saw your post, I decided to do it myself in virtual lab..

the battery used is 6V
Both resistors are 3ohms as in question

Here is what I got:


When switch is open, you get this:

The ammeter tell its 1A.


When switch is closed you get this:

the ammeter is 2A

It was an animation, and you were right snowbrood, the current didnt seem to flow through the other resistor..


Now I am more confused then I was before.
Doesnt this collapse the paralell circuit resistance thingy ??

ANyone?

 

[abcde]

just wanna quick confirmation:

When switch is open, current is 1.
When switch is closed, current is 1.8,

and that in the question they have rounded off 1.8 to 2.

The answer is B. When the switch is open, current flows through both resistors (it has to in order to complete the circuit. There's no other way.)
R = V/I
=> I = V/R = 6/(3+3) = 1 A.
When the switch is closed, there are two pathways through which current can pass, one being through both resistors (as in the first case) and the other through just one resistor. The current will pass through just one resistor as it easier to do so. (This is the reason why short-circuiting exists.) So, I = 6/3 = 2 A.

P.S. In no sense is this a parallel circuit when the switch is closed.

 

[Anon]

Thank you veeryy much...

But still one question:

The current would go through path of least resistance, right?
So how does paralell circuit exist? Because current goes through both pathways in it..

 

[snowbrood]

there is no parallel circuit here buddy its series one.. once the switch in on the current flows through only one resistor...

 

[snowbrood]

even abcde said the same thing i think u failed to notice that

 

[Silent Hunter]

Thank you veeryy much...

But still one question:

The current would go through path of least resistance, right?
So how does paralell circuit exist? Because current goes through both pathways in it..

general question or talking about this specific one?

 

[Anon]

general

 

[abcde]

Thank you veeryy much...

But still one question:

The current would go through path of least resistance, right?
So how does paralell circuit exist? Because current goes through both pathways in it..

Current will go through path of zero/negligible resistance if such path exists.
Consider two examples:
1) There are two pathways; one with zero (negligible) resistance and the other with some resistance. The current will flow through the one with zero resistance.
(This is how short circuiting happens). In the MCQ above, current flows through the switch as it has negligible resistance, eliminating any need for a parallel circuit to exist.
2) There are two pathways with different resistances. Current does NOT just flow through the one with the smaller resistance. It flows through both, hence a parallel circuit exists. But the magnitude of the current is larger for the one with smaller resistance.

 

[SalmanPakRocks]

u guys i still have confusion.
I 100% agree that when the switch is open so the current will be 1A
=> I = V/R = 6/6 = 1A
but what will be the working of second?
I mean won't the current be shared as now we are making it a parallel circuit.
when current will pass through 1st resistor the current will be 2A
=> I=V/R =6/3 =2A
but when it comes to the second it gets shared into 1:1 ratio as its a parallel circuit.?

 

[SalmanPakRocks]

Thank you veeryy much...

But still one question:

The current would go through path of least resistance, right?
So how does paralell circuit exist? Because current goes through both pathways in it..

Current will go through path of zero/negligible resistance if such path exists.
Consider two examples:
1) There are two pathways; one with zero (negligible) resistance and the other with some resistance. The current will flow through the one with zero resistance.
(This is how short circuiting happens). In the MCQ above, current flows through the switch as it has negligible resistance, eliminating any need for a parallel circuit to exist.
2) There are two pathways with different resistances. Current does NOT just flow through the one with the smaller resistance. It flows through both, hence a parallel circuit exists. But the magnitude of the current is larger for the one with smaller resistance.

Are u sure about it ?
I mean because won't the current pass through second resistor ??