An experiment is conducted to determine the internal resistance (r) of a cell using a potentiometer. A known emf of E = 1.5 V is connected to the potentiometer. The balancing length for the cell is L = 60 cm, and the total length of the potentiometer wire is Ltotal = 100 cm. If the internal resistance of the potentiometer is negligible, calculate the internal resistance of the cell.
0.6 volt
0.5 volt
1.0 volt
0.7 volt
Given values:
Emf of the cell (E) = 1.5 V
Balancing length (L) = 60 cm
Total length of the potentiometer wire (Ltotal) = 100 cm
The potential difference across the length L of the potentiometer wire is given by:
The potential difference V is also equal to the product of the current (I) and the total resistance (R) in the circuit:
V = I.R
The total resistance R can be written as the sum of the internal resisitance (r) of the cell and the resistance (Rpot) of the potentiometer wire:
R = r + Rpot
Substitute the expressions for V and R and solve for r:
Step 1: Calculate the resistance of the potentiometer wire:
Step 2: Calculate the internal resistance r of the cell:
Step 3: Substitute the given values and calculate r:
The internal resistance of the cell is 0.5 V.
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