Where is the point when the potential is zero?

AI Thread Summary
The discussion focuses on finding points along the line between two charges where the electric potential is zero. The initial attempt yielded a distance of 2.76 cm, but the user encountered issues with the computer's response indicating missing values. Clarification was provided that the potential equation should account for the absolute distances from both charges. The user later calculated a second potential point at 0.0403 m but faced further errors related to the sign and values in the denominator. The conversation emphasizes careful attention to the formula and the correct interpretation of distances in the context of electric potential.
asz304
Messages
107
Reaction score
0

Homework Statement


A 2.96 uC and a -1.85 uC charge are placed 4.48 cm apart. At what points along the line joining them is the potential zero? Let V = 0 at r = infinity and enter the smaller distance first.


Homework Equations



V = k*q/r


The Attempt at a Solution



V(total) = 0 = kq1/x + kq2/(0.0448 - x)

x = q1*d/(q1 - q2)

x = 2.76*10^-2 m


Is there something that I'm missing? The computer says that I'm missing another value..

Thanks
 
Physics news on Phys.org
"r" means distance, not difference between coordinates in the formula for the potential. If q1 is placed in the origin and q2 is on the positive x-axis at d, You should have written your equation as q1/|x|+q2/|x-d|=0. There are three possibilities to discuss: x>d, (the point is on the right from q2) 0<x<d (the point is between q1 and q2) and x<0 (the point is on the left from q1).

ehild
 
I came with a second answer of 0.0403 m

x(2) = -q1d/(-q1-q2)

but the computer says I'm giving it the wrong answer. Is there something that I'm doing wrong?
 
x(2)=-2.96/(-2.96+1.85) *4.48. It is not 4.03 cm!

ehild
 
Thanks. I knew I'll mess something up with the denominator because of "-q2" and q2 = 1.85*10^-6 C.
 
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Correct statement about a reservoir with an outlet pipe'
The answer to this question is statements (ii) and (iv) are correct. (i) This is FALSE because the speed of water in the tap is greater than speed at the water surface (ii) I don't even understand this statement. What does the "seal" part have to do with water flowing out? Won't the water still flow out through the tap until the tank is empty whether the reservoir is sealed or not? (iii) In my opinion, this statement would be correct. Increasing the gravitational potential energy of the...
Back
Top