1. Tardigrade
  2. Question
  3. Physics
  4. Consider a region in free space bounded by the surfaces of an imaginary cube having sides of length ‘a’ as shown in the diagram. A charge +Q is placed at the centre ‘O’ of the cube. P is such a point outside the cube that the line OP perpendicularly intersects the surface ABCD at R and also OR = RP = a/2. A charge +Q is placed at point P also. What is the total electric flux through the five faces of the cube other than ABCD ?

Question Error Report

Thank you for reporting, we will resolve it shortly

Back to Question

Q. Consider a region in free space bounded by the surfaces of an imaginary cube having sides of length ‘$a$’ as shown in the diagram. A charge $+Q$ is placed at the centre ‘$O$’ of the cube. $P$ is such a point outside the cube that the line $OP$ perpendicularly intersects the surface $ABCD$ at $R$ and also $OR = RP = a/2$. A charge $+Q$ is placed at point $P$ also. What is the total electric flux through the five faces of the cube other than $ABCD$ ?Physics Question Image

WBJEEWBJEE 2018Electric Charges and Fields

Solution:

For surface $A B C D$ electric flux is zero. Because at surface $A B C D$ net electric field is zero. Using Gauss's law,
$\oint \Sigma \cdot d S=\frac{Q_{\text {in }}}{\varepsilon_{0}}$
Electric flux through the five faces of the cube,
$\phi_{B}=\frac{Q}{\varepsilon_{0}}$