JEE Main 2022PhysicsCurrent ElectricityHardNumerical

JEE Main 2022 — Current Electricity Question with Solution

JEE Main 2022 (28 Jul Shift 1)

Question

As shown in the figure, a potentiometer wire of resistance 20 Ω and length 300 cm is connected with resistance box (R.B.) and a standard cell of emf 4 V. For a resistance 'R' of resistance box introduced into the circuit, the null point for a cell of 20 mV is found to be 60 cm. The value of 'R' is _____ Ω.

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Show full solutionCorrect answer: 780
Correct answer
780

Step-by-step explanation

Given here, l=300 cm, Rw=20 Ω and ε=4 V.

Using the relation, E2=l1l2E1, we have

E=ACABVA-VB

∴20×10-3=60300×4×20R+20⇒5×10-3=4R+20

∴R=780 Ω

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About this question

This is a previous-year question from JEE Main 2022, 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.