## anonymous 4 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. anonymous

sounds like physics bud

2. anonymous

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

3. anonymous

if you want me to help. . .

4. anonymous

Do you know the formula for electric field?

5. anonymous

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

6. anonymous

$E= kq/r^2$

7. anonymous

okay. then?

8. anonymous

|dw:1340433733455:dw|

9. anonymous

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

10. anonymous

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

11. anonymous

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

12. anonymous

okay. i think it is the length.

13. anonymous

|dw:1340433904871:dw|

14. anonymous

okay.

15. anonymous

hmm i think thats it.

16. anonymous

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

17. anonymous

sorry i dont know.

18. anonymous

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

19. anonymous

can you do that?

20. anonymous

52.5 * sqrt of 2 ?

21. anonymous

yes = ?

22. anonymous

74.24

23. anonymous

but why sqrt of 2 ?

24. anonymous

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

25. anonymous

okay sure.

26. anonymous

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

27. anonymous

its 37.12

28. anonymous

okay so now we can use our formula.

29. anonymous

okay.

30. anonymous

E=(kq)/r^2

31. anonymous

our k is 9x10^9 ?

32. anonymous

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

33. anonymous

oh but can we use 9x10^9 ?

34. anonymous

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

35. anonymous

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

36. anonymous

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

37. anonymous

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

38. anonymous

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

39. anonymous

so lets get started

40. anonymous

okay sure lets get started

41. anonymous

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

42. anonymous

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

43. anonymous

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

44. anonymous

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

45. anonymous

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

46. anonymous

therefore 45E-6

47. anonymous

why is the exponent is -6 ?

48. anonymous

i just told you, because the units are in uC

49. anonymous

that little "u" mean E-6

50. anonymous

oh yeah

51. anonymous

52. anonymous

then the C means coulombs?

53. anonymous

correct

54. anonymous

0.00079

55. anonymous

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

56. anonymous

yup i did

57. anonymous

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

58. anonymous
59. anonymous

let me check

60. anonymous

E means exponent right?

61. anonymous

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. anonymous

its -27uC

63. anonymous

right, -27uC still the same answer.

64. anonymous

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

65. anonymous

okay thank you so much.

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