Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main202621 January 2026Evening ShiftPhysicsCurrent ElectricityActual

Two known resistances of R and 2 R and one unknown resistance X are connected in a circuit as shown in the figure. If the equivalent resistance between points A and B in the circuit is X , then the value of X is _ _ _ _ .

Options

  1. A( 3 -1) R
  2. B2( 3 -1) R
  3. C( 3 +1) R
  4. DR

Correct answer

A. ( 3 -1) R

Step-by-step solution

The circuit has 2R and X in series (top branch) parallel to R (bottom branch). The equivalent resistance is R_ eq = (2R + X) R 3R + X = X . Setting up the equation: X(3R + X) = R(2R + X) , which simplifies to X^2 + 2RX - 2R^2 = 0 . Using the quadratic formula: X = -2R 2R 3 2 = R(-1 3 ) . Since resistance must be positive, X = ( 3 - 1)R Ω.

Practice Current Electricity on Quantrex Academy →

More from Current Electricity

A metal wire of cross-sectional area 0.5 mm ^2 and length 100 m is connected across a battery of e.m.f. 2 V and internal resistance 1 . The density, atomic mass and electrical cond 2026As shown in the figure, the resistance of a galvanometer G can be found by the half-deflection method. Here the resistance R₂ is adjusted such that when the key K is closed the def 2026The stored charge in the capacitor in steady state of the following circuit is ________ C. 2026A moving coil of galvanometer when shunted with 2 , resistance gives a full scale deflection for a current of 500 mA. When a resistance of 470 , is connected in series it gives a f 2026Two cells of emfs 1 V and 2 V and internal resistance 2 , and 1 , , respectively connected in parallel, gave a current of 1 A through an external resistance. If the polarity of one 2026Refer to the circuit diagram given below. The heat generated across the 6 , resistance in 100 second is 100 J. The value of is _______. (Nearest integer) 2026In an experiment to determine the resistance of a given wire using Ohm's law, the voltmeter and ammeter readings are noted as 10 V and 5 A , respectively. The least counts of voltm 2026Under steady state condition the potential difference across the capacitor in the circuit is _______ V. 2026 Full Current Electricity list All JEE Main PYQs