Question

(1) At a point in space, an electrostatic force acts downward on a proton. The direction of the electric field at that point must be (a) horizontally to the right(b) horizontally to the left (c) vertically up (d) vertically down Two charges originally separated by a certain distance are moved farther apart, until the force between them has decreased by a factor of 10. Is the new distance (a) less than 10 times the original distance (b) equal to 10 times the original distance (c) greater than 10 times the original distance. (d) unchanged (e)undetermined by the data. (3) Three equal-magnitude point charges of varying signs are placed at three of the corners of a square of side d as shown in the figure. Which one of the arrows shown represents the direction of the net electric field at the vacant corner of the square? + (a) A (6) B (c) C (d) D

Answer 1

1. As force on a charge in electric field is given by

F=qE

So for positive charge the direction of force will be in the direction. Of electric field so,

Electric field will be vertically downward.

2.force between two charges are given by

As force is inversely proportional to the square of separation between the two charges so,

F_1//F₂=(r₂)²/(r₁)²

force in second situation=

force in first situation /10 ( GIVEN IN QUESTION)

So,. F₂= F₁/10

F₁/F₂=10

So r₂/r₁= 10^1/2 = √10 = 3.16

So r₂= 3.16 r₁ = ( less than 10 times the original distance