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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceDiagram basedMediumCalculation

JEE Main 25 July 2021, Shift 2, Physics Q20

Question 20 of 90 in this shift, Physics question 20 of 30, Section A.

In the given potentiometer circuit arrangement, the balancing length AC is measured to be 250 cm. When the galvanometer connection is shifted from point (1) to point (2) in the given diagram, the balancing length becomes 400 cm. The ratio of the emf of two cells, ε1ε2\frac{\varepsilon_1}{\varepsilon_2} is :

The figure, in words

Potentiometer circuit: wire AB with jockey/contact C on it; the top branch has a key K, a cell marked V and a rheostat connected between A and B. Galvanometer G connects from C down to the common junction between two cells ε1\varepsilon_1 and ε2\varepsilon_2 (in series along the bottom); the end A is connected by a wire to terminal (1) (the free end of the ε1\varepsilon_1 side) and terminal (2) is the free end of the ε2\varepsilon_2 side.
  1. (1)85\frac{8}{5}
  2. (2)53\frac{5}{3}Official answer
  3. (3)32\frac{3}{2}
  4. (4)43\frac{4}{3}

Official answer

Option 2

NTA final key.

Chapter
Current Electricity
Topic
Potentiometer
Idea tested
Comparing EMF of Two Cells

Same idea in other shifts

Asked 4× in all
  1. 25 Jul 2022, Shift 2 · Q55In a potentiometer arrangement, a cell of emf 1.20 V gives a balance point at 36 cm length of wire. This cell is now replaced by another…EasyNumerical value
  2. 24 Jun 2022, Shift 1 · Q59In a potentiometer arrangement, a cell gives a balancing point at 75 cm length of wire. This cell is now replaced by another cell of…EasyNumerical value
  3. 25 Feb 2021, Shift 1 · Q30In the given circuit of potentiometer, the potential difference E across AB (10 m length) is larger than E1E_1 and E2E_2 as well. For key…EasyNumerical valueHas 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.