Two charges are placed at the corners of a square

[remchu123]

Electric Potential !

Homework Statement

Two charges are placed at the corners of a square. One charge, 4.0μC, is fixed to one corner and another, -6.0μC, is fixed to the opposite corner. What charge would need to be placed at the intersection of the diagonals of the square in order to make the potential difference zero at each of the two unoccupied corners?

Homework Equations

V= kq /r

The Attempt at a Solution

Vtot = V1 + V2 + V3

but then i realized that 3rd charge is unknown where it is, i just don't know how i should approach this problem? help. =[

 

[tiny-tim]

welcome to pf!

hi remchu123! welcome to pf!

3rd charge is unknown where it is, i just don't know how i should approach this problem? help. =[

call the 3rd charge (the one in the centre) q, then proceed as usual …

show us what you get ​

 

[SammyS]

Homework Statement

Two charges are placed at the corners of a square. One charge, 4.0μC, is fixed to one corner and another, -6.0μC, is fixed to the opposite corner. What charge would need to be placed at the intersection of the diagonals of the square in order to make the potential difference zero at each of the two unoccupied corners?

Homework Equations

V= kq /r

The Attempt at a Solution

Vtot = V1 + V2 + V3

but then i realized that 3rd charge is unknown where it is, i just don't know how i should approach this problem? help. =

Hello remchu123 . Welcome to PF !

That's why there are variables.

Let the charge at the center have a charge of Q or q.

 

[remchu123]

V1 + V2 + V3 =0

kq1 /d + kq2 /d + kq3 /d (route)2 over 2= 0

then i solved for q3 and i got -2.8x 10^-6 C

but the answer is -1.4 x 10^-6C

which means i forgot half somewhere..

thanks though! i think i can handle it!

wish me luck in physics 12 exam tomorrow! ahha

i'll very likely need all of your "ki"s ( DBZ reference? lol)

 

[tiny-tim]

hi hremchu123!

(btw, it's "root" not "route" )

you just got confused about the distance …

it's d/√2, not d√2