Please help: Calculate the electric field at the center of a square 52.5cm on a side if one corner is occupied by a +45uC charge and the other three occupied by -27uC charges.

- anonymous

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- baldymcgee6

sounds like physics bud

- baldymcgee6

but i will help you anyway. you just need to find the NET electric field.

- baldymcgee6

if you want me to help. . .

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## More answers

- baldymcgee6

Do you know the formula for electric field?

- anonymous

is it E=F(R)/Q ??

- baldymcgee6

\[E= kq/r^2\]

- anonymous

okay. then?

- baldymcgee6

|dw:1340433733455:dw|

- baldymcgee6

does the question say the side length of the square is 52.5cm?

- anonymous

The question say: "at the center of a square 52.5cm on a side if one corner is occupied by a +45uC charge..."

- baldymcgee6

okay, i'm going to assume the "side length" is 52.5cm

- anonymous

okay. i think it is the length.

- baldymcgee6

|dw:1340433904871:dw|

- anonymous

okay.

- anonymous

hmm i think thats it.

- baldymcgee6

you need the length from the corner to the charges. do you know how to find that?

- anonymous

sorry i dont know.

- baldymcgee6

okay, if we have the side length of 52.5cm, to find the diagonal length we multiply this by \[\sqrt{2}\]

- baldymcgee6

can you do that?

- anonymous

52.5 * sqrt of 2 ?

- baldymcgee6

yes = ?

- anonymous

74.24

- anonymous

but why sqrt of 2 ?

- baldymcgee6

because a square is in the form of x^2+y^2=2.. you can look into it later, and just trust me.

- anonymous

okay sure.

- baldymcgee6

haha, k... so that 74.25cm is the diagonal length, we divide this by 2 to give us the corner to center length

- anonymous

its 37.12

- baldymcgee6

okay so now we can use our formula.

- anonymous

okay.

- baldymcgee6

E=(kq)/r^2

- anonymous

our k is 9x10^9 ?

- baldymcgee6

close enough, in physics we typically use 8.99 x 10^9

- anonymous

oh but can we use 9x10^9 ?

- baldymcgee6

we have to calculate each individual electric field. sure, it is close enough.

- anonymous

okay. then our Q is what? our R is 37.12 ?

- baldymcgee6

our q is the charge, there are 4 different charges. +45uC and -27uC, -27uC, -27uC

- anonymous

so we will use the four different charges? one by one?

- baldymcgee6

we will do two separate computations as three of them will be the same (-27uC)

- baldymcgee6

so lets get started

- anonymous

okay sure lets get started

- baldymcgee6

fill this in with what we know: E=(kq)/r^2

- baldymcgee6

or just do it on you're calculator and tell me the two answers

- anonymous

E=(9x10^9) (+45uC)/37.12 ?

- baldymcgee6

close... E=(9x10^9*45E-6)/(37.12)^2
dont forget to square the denominator

- baldymcgee6

and also remember the units for the charge is in micro coulombs

- baldymcgee6

therefore 45E-6

- anonymous

why is the exponent is -6 ?

- baldymcgee6

i just told you, because the units are in uC

- baldymcgee6

that little "u" mean E-6

- anonymous

oh yeah

- baldymcgee6

okay, so what your answer?

- anonymous

then the C means coulombs?

- baldymcgee6

correct

- anonymous

0.00079

- baldymcgee6

you used this?
E=(9x10^9*45E-6)/(37.12)^2

- anonymous

yup i did

- baldymcgee6

well i'm afraid that is wrong, you must have typed it in wrong

- baldymcgee6

http://www.wolframalpha.com/input/?i=%28%289x10%5E9%29%2845E-6%29%29%2F%2837.12%29%5E2

- anonymous

let me check

- anonymous

E means exponent right?

- baldymcgee6

k dude, you take way to long. I need to sleep. You should get a value of 293.55 N/C for the +45uC
and you should get -176.13 N/C for the -26uC

- anonymous

its -27uC

- baldymcgee6

right, -27uC still the same answer.

- baldymcgee6

i think you should be able to do it from here.. i've been helping you for over an hour.

- anonymous

okay thank you so much.

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