In a potentiometer experiment, the balancing length of a cell is 560 cm. When an external resistance of 10 Ω is connected in parallel to the cell, the balancing length chages by 60 cm. The internal resistance of a cell is

Question

In a potentiometer experiment, the balancing length of a cell is 560 cm. When an external resistance of 10 Ω is connected in parallel to the cell, the balancing length chages by 60 cm. The internal resistance of a cell is, 1.4 Ω, 1.6 Ω, 0.12 Ω, 1.2 Ω

MARKS App · Accepted Answer

Consider a cell of emf E and balancing length l 1 E = k l 1 The potential difference is balanced by length l 2 . V = k l 2 The internal resistance of the cell is given by r = E - V V R = E V - 1 R = l 1 l 2 - 1 R = 560 560 - 60 - 1 10 = 56 50 - 1 10 = 6 5 = 1.2 Ω

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