Physics: Post your doubts here!

[Student12]

Which is the best physics Alevel textbook to study from ? Need help badly !

 

[insomniac]

Which is the best physics Alevel textbook to study from ? Need help badly !

this if u want to the point understanding

 

[Musab100]

can anyone help me in these questions
oct nov 2012 paper 22 q5 partb and q7 part e

 

[insomniac]

question 5(b)

 

[Musab100]

question 5(b)

thanks a lot
can u please also help me in q7 part e ???

 

[insomniac]

thanks a lot
can u please also help me in q7 part e ???

2.7 x 10^13 times per second*

 

[insomniac]

u didnt get the attachment image?

 

[Musab100]

no sorry i got it sorry

 

[insomniac]

thanks a lot
can u please also help me in q7 part e ???

 

[insomniac]

thats fine

 

[Musab100]

u didnt get the attachment image?

how u got this eq 60w=n*13.8*1.60*10^19*10^6 J
???

 

[Musab100]

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

can u help me in this part plzz

 

[insomniac]

by putting energies equal

 

[Musab100]

can anyone help me in this question
???

 

[1357911]

can anyone help me in this question
???

ai - Apply Kirchoffs First Law... Current Flowing towards the junction is the sum of the currents flowing away from the junction. I1 and I3 are moving towards the junction so it will be. I2=I1=I3
aii - Kirchoff's second Law. Sum of Emf is equal to the sum of P.d's. the p.d=V=IR.
so E = (Ir + IR)
see the circuit asked in the queation Only one part that is the current emf and the resistance only in the loof HBJFGH is asked. So it will be E1 = (I1 x (r1+R1/2)+(I2 x R2/2) (R1/2 because there are two current for bot the resistors... current will be divided between I1 and I2) and addition because both the currents are flowing in the same direction.

 

[1357911]

can anyone help me in this question
???

aiii - Again apply kirchoff's tsecond law.
this time they have asked for the whole circuit. i.e. E1, E2, r1, r2, R1, R2, I1 and I3 in the loop HBCDJFGH. Notice that I2 is not asked.
so first see the emf. it will be. E1-E2. Negative because the currents for both of them are flowing in opposite directions.
Applying Kirchoff's second law
E1-E2 = (I1 x (r1+R1 + R2/2) - (I3 x r2) ( R2/2 because remember I2 is also flowing for I2) and negative because E2 is in the opposite direction.

 

[Musab100]

aiii - Again apply kirchoff's tsecond law.
this time they have asked for the whole circuit. i.e. E1, E2, r1, r2, R1, R2, I1 and I3 in the loop HBCDJFGH. Notice that I2 is not asked.
so first see the emf. it will be. E1-E2. Negative because the currents for both of them are flowing in opposite directions.
Applying Kirchoff's second law
E1-E2 = (I1 x (r1+R1 + R2/2) - (I3 x r2) ( R2/2 because remember I2 is also flowing for I2) and negative because E2 is in the opposite direction.

thanks i want to ask few things
1. why E1-E2 WHY NOT E2 -E1 ???
2. I dont get why I3*R2/2 is -ve ???

 

[1357911]

thanks i want to ask few things
1. why E1-E2 WHY NOT E2 -E1 ???
2. I dont get why I3*R2/2 is -ve ???

Look at the directions of the currents flowing from E2 and E1. The current from E1 is clockwise and the current flowing from E2 is anticlockwise. i.e. in totally in opposite directions. Assume the clockwise direction to be positive and anticlockwise to be negative always.
Reffereng to -E2... it shuld be negative. Again see the direction. The direction i.e. The arrows are very very important.

 

[Afza Munir]

Hi there,
i have a lil confussion here if anyone can solve it for me regardin physics. Actually i em doin my A level's and i need to take physics just to get admission in my country for futher studies but i personally dont like physics so i was planin that i will study physics in AS level (11) but will not appear in the board exam may/june session then when i will be done with my A2 level (12) at that time i will give both AS level and A2 level papers so is it alright to do so or it might be hard for me ?
em doin this cuz i dont wonna mess up with my bio and chemistry subject grades

 

[BAOOZHEN]

in the practical how do you find percentage uncertainty in angles and everything also how do you find gradient and y-intercept from the graphs,