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Concepts Of Physics MCQ Edition [Volume 2]
Exam
Concepts Of Physics MCQ Edition [Volume 2]
Subject
Physics
Chapter
Electric Current in Conductors

Concepts Of Physics MCQ Edition [Volume 2] · Physics · Electric Current in Conductors

Two nonideal batteries are connected in series. Evaluate the...

Two nonideal batteries are connected in series. Evaluate the following statements:
(A) The equivalent emf is greater than either of the two emfs.
(B) The equivalent internal resistance is less than either of the two internal resistances.

Options

  1. ABoth A and B are true
  2. BB is true but A is incorrect
  3. CA is true but B is incorrect
  4. DBoth A and B are incorrect

Correct answer

D. Both A and B are incorrect

Step-by-step solution

When two nonideal batteries of emfs E1E_1 and E2E_2 and internal resistances r1r_1 and r2r_2 are connected in series, the equivalent internal resistance is given by req=r1+r2r_{eq} = r_1 + r_2.

Since r1>0r_1 > 0 and r2>0r_2 > 0, the equivalent internal resistance reqr_{eq} is strictly greater than both r1r_1 and r2r_2. Therefore, statement B is incorrect.

The equivalent emf of the series combination depends on the polarity of the connection. If the batteries are connected such that they aid each other, Eeq=E1+E2E_{eq} = E_1 + E_2. However, if they are connected with opposing polarities, Eeq=∣E1−E2∣E_{eq} = |E_1 - E_2|. In the opposing case, the equivalent emf is less than the larger of the two individual emfs. Therefore, statement A is not universally true and is incorrect.

Thus, both statements A and B are incorrect.
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