Question

1. What are the magnitude and direction of the electric field at the center of a square with side=5.0 cm if there are 4 point charges of equal magnitude at the corners: at top left and lower right q is positive while at top right and lower left q is neg. q has magnitude 1.0 x 10 raised to -8 C.

Answer 1

Electric field is given by:

E = kQ/R^2

Direction of electric field is away from positive charge and toeards the negative charge.

Now net electric field will be

E = E1 + E2 + E3 + E4

Now direction due to charge on lower left negative side will be towards the center of square in NE direction.

Now direction due to charge on upper right negative side will be towards the center of square in SW direction.

Now direction due to charge on upper left positive side will be away from the center of square in NW direction.

Now direction due to charge on lower right positve side will be towards the center of square in SE direction.

Now we can see that magneitude of each force will be equal, since Q and R are same and k is constant, So

So,

|E1| = |E2| = |E3| = |E4|

E1 = -E3 & E2 = -E4

which means

Enet = 0 N/C

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