COMEDK · Physics · 19. Current Electricity

In the given circuit, an ideal voltmeter connected across \(6\Omega\) reads 5V. The internal resistance r of each cell is:

A \(0.01\ \Omega\)
B \(0.1\ \Omega\)
C \(0.5\ \Omega\)
D \(0.2\ \Omega\)

Verified Solution

Answer & Solution

Correct Answer

(D) \(0.2\ \Omega\)

Step-by-step Solution

Detailed explanation

The equivalent resistance of the upper branch is \(9\ \Omega + 3\ \Omega = 12\ \Omega\). The equivalent resistance of the parallel combination is \(R_p = \dfrac{12 \times 6}{12 + 6} = 4\ \Omega\). The voltage across the parallel combination is given as \(V_p = 5\text{ V}\). The…

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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