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Saturday, 31 October

JEE Main 2022 · PhysicsNumerical answerNumerical valueHardMulti-step

JEE Main 28 July 2022, Shift 1, Physics Q55

Question 55 of 90 in this shift, Physics question 25 of 30, Section B.

As shown in the figure, a potentiometer wire of resistance 20 Ω\Omega 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\Omega.

The figure, in words

Potentiometer circuit: wire AB of resistance 20 ohm, length 300 cm; driver cell 4 V in series with resistance box R.B. (R) connected across A and B; a 20 mV cell with galvanometer connected at A with jockey on the wire (null point).

Official answer

780

NTA final key (2022 Session 2).

Chapter
Current Electricity
Topic
Potentiometer
Idea tested
Potential Gradient Calculation

Same idea in other shifts

Asked 5× in all
  1. 26 Jul 2022, Shift 2 · Q59A potentiometer wire of length 300 cm is connected in series with a resistance 780 Ω\Omega and a standard cell of emf 4V. A constant…MediumNumerical value
  2. 24 Jun 2022, Shift 2 · Q53A potentiometer wire of length 10 m and resistance 20 Ω\Omega is connected in series with a 25 V battery and an external resistance 30…MediumNumerical value
  3. 8 Jan 2020, Shift 1 · Q20The length of a potentiometer wire is 1200 cm and it carries a current of 60 mA. For a cell of emf 5 V and internal resistance of 20…MediumSingle correct
  4. 2 Sep 2020, Shift 2 · Q20A potentiometer wire PQ of 1 m length is connected to a standard cell E1_1. Another cell E2_2 of emf 1.02 V is connected with a…EasyDiagram basedHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.