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## Homework Statement

a square of sides 10cm has four charges at each corner starting clockwise from top right they are 5,10,6 and 3nC. Determine the resultant electric field including magnitude and direction at the centre of the square. Owww and the medium is air. Finally what is the force on a 6pC placed at this point.

i should probably point out ive never done physics in my life be4 u give me grief....... take pity

## Homework Equations

okay first part im using

kQ/R^2

k= 1/4pi* E0*Er

E0= 8.854*10^-12

Er= 1.005

my value of r is 7.07cm which = 0.0707m

sooooo i have 4 electric fields of;

8945.723 Cm^-1

17892.28 ...

10735.37 ...

5367.68 ....

solving as vectors......

(x)= 5367.68cos45 + 10735.37cos45 - 17892.28cos45 - 8945.723cos45

= 7590.55 to the left

(y)= 10735.37sin45+17892.28sin45 - 8945.723sin45 - 5367.68sin45

= 2530 upwards

gives me a magnitude of 8000 Cm^-1

at an angle of 18.43

then the force is

q*E = 6*10^-9 *8000 = 4.8*10^-5N

Thanks for any help, Lee.