Biology; Chemistry; Physics: Post your doubts here!

[Saad Mughal]

and most last question?

What answer are you getting here?

 

[ZaqZainab]

shoooooookriyaaa!

You are welcome!

 

[Suchal Riaz]

What answer are you getting here?

by v=ir i get 68ohms
answer is 292. er says that most students forgot to subtract. subtract what?

 

[Saad Mughal]

by v=ir i get 68ohms
answer is 292. er says that most students forgot to subtract. subtract what?

I also got 68 ohms but the current given is for 1.7 V, the circuit is of 9 V.
They want us to calculate for the whole circuit, R=9/0.025 (current is same throughout).
Then subtract 68 ohms from this. I have no idea why.

 

[asma tareen]

subtract the voltage 9-1.7 and calculate again

 

[Saad Mughal]

by v=ir i get 68ohms
answer is 292. er says that most students forgot to subtract. subtract what?

I think I've got it,
The LED has a potential difference of 1.7 V,
The e.m.f. is 9 V,
The resistor hence has a potential difference of 9-1.7=7.3 V,
Minimum Resistance = 7.3/0.025 = 292 ohms.

 

[asma tareen]

I think I've got it,
The LED has a potential difference of 1.7 V,
The e.m.f. is 9 V,
The resistor hence has a potential difference of 9-1.7=7.3 V,
Minimum Resistance = 7.3/0.025 = 292 ohms.

i dint have a logic for my ans but now i got it

 

[Suchal Riaz]

I think I've got it,
The LED has a potential difference of 1.7 V,
The e.m.f. is 9 V,
The resistor hence has a potential difference of 9-1.7=7.3 V,
Minimum Resistance = 7.3/0.025 = 292 ohms.

i can not believe how silly i m. i have no right to live in this planet any more
they gave p.d of lamp but i calculator R of resistor by p.d of lamp. much a silly mistake. my teacher would not even tell me answer but have murdered me.

 

[Saad Mughal]

i can not believe how silly i m. i have no right to live in this planet any more
they gave p.d of lamp but i calculator R of resistor by p.d of lamp. much a silly mistake. my teacher would not even tell me answer but have murdered me.

The key again. I directly went to this part and did not even see the circuit diagram! READ QUESTIONS PROPERLY. Whoever said that was a genius.

 

[Saad Mughal]

i dint have a logic for my ans but now i got it

Wow. You're brilliant

 

[Suchal Riaz]

i dint have a logic for my ans but now i got it

ur logic is correct asma. we are calculating R of resistor not lamp. so we need to subtract to get p.d or resistor. thanx.

 

[asma tareen]

Wow. You're brilliant

i know

 

[Suchal Riaz]

The key again. I directly went to this part and did not even see the circuit diagram! READ QUESTIONS PROPERLY. Whoever said that was a genius.

it was probably me who said it.

 

[Saad Mughal]

it was probably me who said it.

Oh please.
I've been hearing this since class VII.
Never once have I bothered listening.

 

[asma tareen]

ur logic is correct asma. we are calculating R of resistor not lamp. so we need to subtract to get p.d or resistor. thanx.

hmmm u're welcome

 

[Khadija_1234]

I NEVER get reversible equation...and then I stopped bothering because I didn't find any question on them. any important question regarding reversible reactions u have seen? and if u could please tell me what are the main points to be grasped in order to get hold of the topic :-/ and explain them a bit too like what is state of equilibrium n stuff and how will this knowledge be tested in the exam...

there are some questions related to reversible reactions in MCQs and in paper 2 as well, another question is in oct/nov 2008 and Usama has explained almost everything i guess and you should also know that adding catalyst increases the rate of both, forward and backward reaction. And this knowledge can be tested in the questions of haber and contact processes

 

[TheStallion-Reborn]

Yeah but from what I remember they also say that it is the hydrogen that pops not the splint :/ Or something like that So the word have to be really really clear :S

hydrogen burns, splint extinguishes and a pop sound is there.

 

[TheStallion-Reborn]

If I'm not mistaken, then the answer is C. 32 g.

clash!

 

[Saad Mughal]

clash!

Let's just see what the answer is then.

 

[TheStallion-Reborn]

Let's just see what the answer is then.

n whu turns out to be the BAAP!