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JEE Main20207 Jan 2020Evening ShiftPhysicsCurrent ElectricityActual

The balancing length for a cell is 560 c m in a potentiometer experiment. When an external resistance of 10 Ω is connected in parallel to the cell, the balancing length changes by 60 c m . If the internal resistance of the cell is n 10 Ω , where n is an integer then value of n is ________

Correct answer

0

Step-by-step solution

Let the emf of cell is ε internal resistance is ' r ' and potential gradient is x . Only cell connected: E = 560 x     - - - - - 1 After connecting the resistor E × 10 10 + r = 500 x       - - - - - - 2 From 1 and 2 560 x × 10 10 + r = 500 x 56 = 50 + 5 r r = 6 5 = 1.2 Ω so , n = 12

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