Current Electricity

JEE Main level, single correct, medium

317 of 380

Question 317 of 380

The total length of potentiometer wire AB is 50 cm in the arrangement as shown in figure. If PP is the point where the galvanometer shows zero reading then the length APA P is ____\_\_\_\_ cm.

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Answer: (B) 30

In this potentiometer, for zero galvanometer reading, the potential at P must equal the potential at the junction between the 6Ω and 4Ω resistors.
The voltage distribution across the resistors is Vjunction=E×66+4=0.6EV_{junction} = E \times \frac{6}{6+4} = 0.6E from point A.
Since the potentiometer wire is uniform with length 50 cm, the potential distribution is also uniform.
Therefore, APAB=610\frac{AP}{AB} = \frac{6}{10}, giving AP=50×0.6=30AP = 50 \times 0.6 = 30 cm.

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