JEE Main 2019 — Current Electricity Question with Solution
From: JEE Main 2019 (Online) 12th January Morning Slot
Question
In a meter bridge, the wire of length 1 m has a non-uniform cross-section such that, the variation of its resistance R with length is . Two equal resistances are connected as shown in the figure. The
galvanometer has zero deflection when the jockey is at point P. What is the length AP ?
This question includes a diagram. The text above accompanies the figure.
Choose an option
Show full solutionCorrect option: B
Correct answer
B0.25 m
Step-by-step explanation
For the given wire :
dR = C ,
where C = constant.
Let resistance of part
AP is R1 and PB is R2
or R1 = R2
By balanced WSB concept.
Now
R1 = C = C.2.
R2 = C = C.(2 2)
Putting R1 = R2
C2 = C(2 2)
2 = 1
=
i.e. = m 0.25 m
dR = C ,
where C = constant.
Let resistance of part
AP is R1 and PB is R2
or R1 = R2
By balanced WSB concept.
Now
R1 = C = C.2.
R2 = C = C.(2 2)
Putting R1 = R2
C2 = C(2 2)
2 = 1
=
i.e. = m 0.25 m
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This is a previous-year question from JEE Main 2019, covering the Current Electricity chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.