Question

Figure shows a closed surface which intersects a conducting sphere. If a positive charge is placed at the pointe $P$, the flux of the electric field through the closed surface

• A. will remain zero
• B. will become positive
• C. will become negative
• D. will become undefined

Answer 1

The correct option is B will become positive


By induction, the surface of the conducting sphere near the positive charge will become negatively charged and the rear surface will become positively charged as shown in the figure above.

Hence, the charge inside the closed surface increases from zero to some positive value. Let us assume it is $q_{\text{enclosed}}$.

Thus, by Gauss's law flux through the closed surface also increases and become positive.

$\varphi =\frac{q_{\text{enclosed}}}{{\in }_0}>0$ $[\therefore q_{\text{enclosed}}=+ve]$