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In the figure, the potentiometer wire AB of length L and resistance 9r is joined to the cell D of emf ℰ and internal resistance r. The emf of the cell C is ℰ/2 and its internal resistance is 2r. The galvanometer G will show no deflection when the length AJ is(a) 4L/9 (b) 5L/9 (c) 7L/18 (d) 11L/18 |
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Answer» Correct Answer is: (b) 5L/9 In the position of balance, current in AB is i = ℰ/10r . p.d. across AB is i x 9r = 9ℰ/10 . p.d. per unit length of AB is 9ℰ/10L . For balance, ℰ/2 = (AJ) 9ℰ/10L or AJ = 5L/9 . |
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