11. A cubical region of side $a$ has its centre at the origin. It encloses three fixed point charges, $- q$ at $( 0 , - a / 4,0 ) , + 3 q$ at $( 0,0,0 )$ and $- q$ at $( 0 , + a / 4,0 )$. Choose the correct option(s). [Figure] (A) The net electric flux crossing the plane $x = + a / 2$ is equal to the net electric flux crossing the plane $x = - a / 2$. (B) The net electric flux crossing the plane $y = + a / 2$ is more than the net electric flux crossing the plane $y = - a / 2$. (C) The net electric flux crossing the entire region is $\frac { q } { \varepsilon _ { 0 } }$. (D) The net electric flux crossing the plane $z = + a / 2$ is equal to the net electric flux crossing the plane $x = + a / 2$. ANSWER : ACD
Consider the motion of a positive point charge in a region where there are simultaneous uniform electric and magnetic fields $\vec { E } = E _ { 0 } \hat { j }$ and $\vec { B } = B _ { 0 } \hat { j }$. At time $t = 0$, this charge has velocity $\vec { v }$ in the $x$-y plane, making an angle $\theta$ with the $x$-axis. Which of the following option(s) is (are) correct for time $t > 0$ ?
11. A cubical region of side $a$ has its centre at the origin. It encloses three fixed point charges, $- q$ at $( 0 , - a / 4,0 ) , + 3 q$ at $( 0,0,0 )$ and $- q$ at $( 0 , + a / 4,0 )$. Choose the correct option(s).\\
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(A) The net electric flux crossing the plane $x = + a / 2$ is equal to the net electric flux crossing the plane $x = - a / 2$.\\
(B) The net electric flux crossing the plane $y = + a / 2$ is more than the net electric flux crossing the plane $y = - a / 2$.\\
(C) The net electric flux crossing the entire region is $\frac { q } { \varepsilon _ { 0 } }$.\\
(D) The net electric flux crossing the plane $z = + a / 2$ is equal to the net electric flux crossing the plane $x = + a / 2$.
ANSWER : ACD\\