What is the potential of the big drop formed by 1000 charged rain drops?

[devanlevin]

1000 rain drops, each with a charge of "q" and a potential of "v" fall and make one big drop, losing no charge in the process, what is the potential of the big drop

 

[alphysicist]

Hi devanlevin,

1000 rain drops, each with a charge of "q" and a potential of "v" fall and make one big drop, losing no charge in the process, what is the potential of the big drop

What is the formula for the potential in this case?

 

[devanlevin]

i don't know? KQ/r? how do i work this out?

 

[alphysicist]

i don't know? KQ/r? how do i work this out?

That's right; V=kq/r for each of the small drops. Now relate that to kQ/R for the big drop. What do you get?

 

[devanlevin]

i don't know, how do i know what R is??

 

[alphysicist]

i don't know, how do i know what R is??

What geometric quantity is the same in the group of 1000 drops as in the one big drop? The radius of the big drop is not 1000 times the radius of a small drop; but what is 1000 times larger in the big drop as in one of the small drops?

 

[devanlevin]

thanks, that should help,,, volume right

 

[alphysicist]

thanks, that should help,,, volume right

That's right; and with that you can find how much larger the radius of the big drop is compared to the original ones.