When \(10 \mu C\) charge is enclosed by a closed surface, the flux passing through the surface is \(\phi\). Now another \(10 \mu C\) charge is placed inside the r closed surface, then the flux passing through the surface is _________.

A \(4 \phi\)
B \(\phi\)
C \(2 \phi\)
D zero

Verified Solution

Answer & Solution

Correct Answer

(C) \(2 \phi\)

Step-by-step Solution

Detailed explanation

(C)
\(\begin{array}{l}q=10 \mu C \\ \phi=\frac{q}{\varepsilon_0}\end{array}\)
In \(2^{\text {nd }}\) condition total charge enclosed by a closed surface is
\(
\begin{array}{l}
Q=10+10=20 \mu C \\
Q=2 q
\end{array}
\)
Total flux passing through the surface is
\(\begin{aligned} \phi^{\prime} & =\frac{ Q }{\varepsilon_0}=\frac{2 q}{\varepsilon_0} \\ \therefore \quad \phi^{\prime} & =2 \phi \text { (From equation }(1))\end{aligned}\)

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

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