Consider a uniform electric field \(\overrightarrow{ E }=3 \times 10^3 \hat{k} NC ^{-1}\). The electric flux of this field through a square of 20 cm on a side whose plane is parallel to \(y z\) plane is ________ \(Nm ^2 C ^{-1}\).

A zero
B 90
C 60
D 120

Verified Solution

Answer & Solution

Correct Answer

(A) zero

Step-by-step Solution

Detailed explanation

(A)
Area of square
\(\begin{array}{l}
A=\left(20 \times 10^{-2}\right)^2 \\
A=400 \times 10^{-4} \hat{i} m^2
\end{array}
\)
Flux \(\phi=\overrightarrow{ E } \cdot \overrightarrow{ A }\)
\(\begin{array}{l}\phi=\left(3 \times 10^3\right) \hat{k} \\ \quad\left(400 \times 10^{-4}\right) \hat{i} \\ \phi=0 \quad(\hat{k} \cdot \hat{i}=0)\end{array}\)

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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