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1. Electric Charges and Fields
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Three charges are placed as shown in figure. The magnitude of $q_1$ is $2.00\, \mu C$, but its sign and the value of the charge $q_2$ are not known. Charge $q_3$ is $+4.00\, \mu C$, and the net force on $q_3$ is entirely in the negative $x-$ direction. As per the condition given the sign of $q_1$ and $q_2$ will be

A
$+, +$
B
$+, -$
C
$-, +$
D
$-, -$
Solution

The four possible force diagrams are shown in fig. Only the last picture can result in an electric field in the negative $\mathrm{x}$ – direction.
$\mathrm{q}_{1}=-2.00\, \mu \mathrm{C}, \mathrm{q}_{3}=+4.00 \,\mu \mathrm{C},$ and $\mathrm{q}_{2}>0$
as force on $\mathrm{q}_{3}$ is horizontal
Standard 12
Physics