## alfers101 2 years ago 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.

1. baldymcgee6

sounds like physics bud

2. baldymcgee6

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

3. baldymcgee6

if you want me to help. . .

4. baldymcgee6

Do you know the formula for electric field?

5. alfers101

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

6. baldymcgee6

$E= kq/r^2$

7. alfers101

okay. then?

8. baldymcgee6

|dw:1340433733455:dw|

9. baldymcgee6

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

10. alfers101

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

11. baldymcgee6

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

12. alfers101

okay. i think it is the length.

13. baldymcgee6

|dw:1340433904871:dw|

14. alfers101

okay.

15. alfers101

hmm i think thats it.

16. baldymcgee6

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

17. alfers101

sorry i dont know.

18. baldymcgee6

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

19. baldymcgee6

can you do that?

20. alfers101

52.5 * sqrt of 2 ?

21. baldymcgee6

yes = ?

22. alfers101

74.24

23. alfers101

but why sqrt of 2 ?

24. baldymcgee6

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

25. alfers101

okay sure.

26. baldymcgee6

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

27. alfers101

its 37.12

28. baldymcgee6

okay so now we can use our formula.

29. alfers101

okay.

30. baldymcgee6

E=(kq)/r^2

31. alfers101

our k is 9x10^9 ?

32. baldymcgee6

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

33. alfers101

oh but can we use 9x10^9 ?

34. baldymcgee6

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

35. alfers101

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

36. baldymcgee6

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

37. alfers101

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

38. baldymcgee6

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

39. baldymcgee6

so lets get started

40. alfers101

okay sure lets get started

41. baldymcgee6

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

42. baldymcgee6

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

43. alfers101

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

44. baldymcgee6

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

45. baldymcgee6

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

46. baldymcgee6

therefore 45E-6

47. alfers101

why is the exponent is -6 ?

48. baldymcgee6

i just told you, because the units are in uC

49. baldymcgee6

that little "u" mean E-6

50. alfers101

oh yeah

51. baldymcgee6

52. alfers101

then the C means coulombs?

53. baldymcgee6

correct

54. alfers101

0.00079

55. baldymcgee6

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

56. alfers101

yup i did

57. baldymcgee6

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

58. baldymcgee6
59. alfers101

let me check

60. alfers101

E means exponent right?

61. 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

62. alfers101

its -27uC

63. baldymcgee6

right, -27uC still the same answer.

64. baldymcgee6

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

65. alfers101

okay thank you so much.