Quantrex Quantrex AcademyJEE · NEET · NDA PYQs with solutions Open app
JEE Main2017PhysicsCurrent ElectricityActual

A potentiometer P Q is set up to compare two resistances, as shown in the figure. The ammeter A in the circuit reads 1 . 0 A when the two-way key K 3 is open. The balance point is at a length l 1 cm from P when the two-way key K 3 is plugged in between 2 and 1 , while the balance point is at a length l 2 cm from P when the key K 3 is plugged in between 3 and 1 . The ratio of two resistances R 1 R 2 , is found to be

Options

  1. Al 1 l 1 - l 2
  2. Bl 2 l 2 - l 1
  3. Cl 1 l 1 + l 2
  4. Dl 1 l 2 - l 1

Correct answer

D. l 1 l 2 - l 1

Step-by-step solution

When the key is between 2 and 1 Then, emf V 1 =   I R 1 = x l 1 . When the key is between 3 and 1 Emf, V 2 = I R 1 + R 2 = x l 2 . The ratio of both emf is R 1 R 1 + R 2 = l 1 l 2 On simplifying the above relation, we get the ratio of resitances, R 1 R 2 = l 1 l 2 - l 1 .

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