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When the switch is open in lowermost loop (secondary circuit) of a potentiometer the balance point length is 60 cm. When the switch is closed with a known resistance of
R = 4 ohm, the balance point length decreases to 40 cm. Find the internal resistance of the unknown battery?​

Answer 1

Answer:

2 ohm is the answer .It is the internal resistance

Answer 2

Answer:

The internal resistance is 2 ohm.

Explanation:

• Potentiometer: A potentiometer is a device which is used to measure potential difference in a circuit by varying resistance. A potentiometer basically consists of three terminals.
• Uses: Potentiometer is used for the following purposes-

       (i) For measuring internal resistance of a cell.

       (ii) To measuring potential difference in a circuit.

• Internal resistance calculation: The formula for measuring internal resistance of a cell by using potentiometer is: $r = R\times (\frac{L_1 - L_2}{L_2})$

     Where r = internal resistance,

      R = load resistance = 4 ohm

     $L_1$ = Balancing length without load resistance 60 cm

     $L_2$ = Balancing length with load resistance = 40 cm

    Putting all the values in formula, r = $4 \times \frac{20}{40}$ = 2 ohm

   So, the internal resistance is 2 ohm.

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