PHY5 Jun 05 Thread

2)
g varies with h, as satalite get higher h goes down so weight goes down

Ye phy4 was really hard but phy5 was alright. As for this 48µC thing, wot confused me was it said hence find the charge stored in the capacitor, which meant you had to use your answer from the first question. I think I found the total charge then divided it by 2 but I haven't got a clue if it's right. Dunno why but I had a total memory blank.

What I did was totally different from all of you. I used W=½CV² . But I can't remember the anser I got. I substituted the potential difference and the value of the 4 µF as capacitance.

W=½CV² is used to find the energy but the question was asking to find the charge Q=CV. But wat i cant remeber was whether it asked to find the total charge in the circuit or across the capacitor.

It was to find the charge across the 4 microF capacitor.

How did you guys find the force between the two plates which was x (can't remember the distance) awayfrom each other with the potential difference given?

that was ok i thought although i got 900V (somin in that region- high 900's i think ) for the PD to give the electron the intial speed ?

E=V/d=5kN/C

F=EQ=5kN/C * 1.60x 10^-19 C
=8x10^-16N

i think i got 481 V :/

yeh i got 481 as well and sumit i fort the same about the paper and then TSR here just made everything in2 a big Q mrk. I dnt fink im gna check this site afta exams ever again.

W=½CV² is used to find the energy but the question was asking to find the charge Q=CV. But wat i cant remeber was whether it asked to find the total charge in the circuit or across the capacitor.

Total charge in circuit = the charge on that capicitor anyway.

really are you sure? it had one capacitor in series and two in parallel. I found out the total capacitance in the circuit was 2µF. So my answer of 48µC is right?

48µC was the correct answer (I'm positive), and yes the total capacitance in the circuit would be 2µC