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Saturday, 31 October

JEE Main 2020 · PhysicsMultiple choiceDiagram basedEasyCalculation

JEE Main 2 September 2020, Shift 2, Physics Q20

Question 20 of 75 in this shift, Physics question 20 of 25.

A 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 resistance ‘r’ and switch S (as shown in figure). With switch S open, the null position is obtained at a distance of 49 cm from Q. The potential gradient in the potentiometer wire is :

The figure, in words

Potentiometer circuit: wire PQ drawn horizontally in the middle, P at the left and Q at the right; above it a loop wire connecting P and Q through cell E1. A jockey/contact J (arrow pointing up) touches PQ; from J a wire goes right, down to a galvanometer G (circle with an arrow), then left through a parallel combination of resistor r and switch S, then cell E2, then back to P along the left side.
  1. (1)0.01 V/cm
  2. (2)0.02 V/cmOfficial answer
  3. (3)0.03 V/cm
  4. (4)0.04 V/cm

Official answer

Option 2

NTA final key (Sep 2020).

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. 28 Jul 2022, Shift 1 · Q55As 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…HardNumerical valueHas a figure
  3. 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
  4. 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

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.