Q69 / 90 · JEE Main 2022 (25 Jun Shift 2) · Physics

Two cells of the same EMF E but different internal resistances r1 and r2 are connected in series with an external resistance R as shown in the figure. The terminal potential difference across, the second cell is found to be zero. The external resistance R must then be:

Figure

  • A
    r1r2
  • B
    r1-r2
  • Correct answer
    C
    r2-r1
  • D
    r1+r2

Solution

Figure

In this question we have to find the Terminal potential difference of second cell, we are given the internal resistances of both the cells and an external resistance. Applying the following expression:-

V = E-ir2

⇒0=E-ir2

Applying the expression of current

0=E-2Er1+r2+R·r2

⇒R=r2-r1

Hence, the correct answer is option: 'C'.

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