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JEE Advanced 2022Paper 1
Exam
JEE Advanced
Year
2022
Paper
Paper 1
Subject
Physics
Chapter
Current Electricity

JEE Advanced 2022 · Paper 1 · Physics · Current Electricity

The figure shows a circuit having eight resistances of 1Ω...

The figure shows a circuit having eight resistances of 1Ω each, labelled R1{R}_{1} to R8{R}_{8}, and two ideal batteries with voltages {ε}_{1} = 12V and {ε}_{2} = 6V.

The figure shows a circuit having eight resistances of 1Ω each, labelled R _ 1 to R _ 8 , and two ideal batteries

Which of the following statement(s) is(are) correct?

Options

  1. AThe magnitude of current flowing through R1{R}_{1} is 7.2A7 . 2A.
  2. BThe magnitude of current flowing through R2{R}_{2} is 1.2A1 . 2A.
  3. CThe magnitude of current flowing through R3{R}_{3} is 4.8A4 . 8A.
  4. DThe magnitude of current flowing through R5{R}_{5} is 2.4A2 . 4A.

Correct answer

A. The magnitude of current flowing through R1{R}_{1} is 7.2A7 . 2A.

Step-by-step solution

The figure shows a circuit having eight resistances of 1Ω each, labelled R _ 1 to R _ 8 , and two ideal batteries

Point AA and BB are at same potential so they can be merged/folded.

Now, let& xx and& yy be the current flowing from& 6V6V and& 12V12V batteries.

The current distribution is shown below.

The figure shows a circuit having eight resistances of 1Ω each, labelled R _ 1 to R _ 8 , and two ideal batteries

Applying Kirchhoff's voltage law,

For loop& 1:1:

−12x−12(x+y)−1x+6=0- \dfrac{1}{2}x - \dfrac{1}{2}\left(x + y\right) - 1x + 6 = 0

⇒−2x−y2=−6⇒ - 2x - \dfrac{y}{2} = - 6

⇒−4x−y=−12⇒ - 4x - y = - 12

⇒4x+y=12⋯(1)⇒ 4x + y = 12 ⋯ \left(1\right)

For loop 2:2:

12\dfrac{1}{2} y + 1y + 12 + \dfrac{1}{2}\left( x + y\right) = 0</p><p>32</p><p>\dfrac{3}{2} y + y2+x2=−12\dfrac{y}{2} + \dfrac{x}{2} = -12

2y+x2=−122y + \dfrac{x}{2} = -12

4y+x=−24⋯(2)4y + x = - 24 ⋯ \left(2\right)

Using, \left(2\right) - 4 \times\left(1\right),wehave</p><p>, we have</p><p>4y + x - 16x - 4y= - 24 - 48</p><p></p><p>⇒ - 15x = - 72</p><p></p><p>⇒ x = \dfrac{72}{15}</p><p>Puttinginequation(1)</p><p>Putting in equation \left(1\right),

4(7215)+y=124\left(\dfrac{72}{15}\right) +y = 12

⇒y=12−28815=180−28815=−10815=−7.2A⇒ y = 12 - \dfrac{288}{15}= \dfrac{180 - 288}{15}= \dfrac{- 108}{15} = -7 . 2A

Now, current in R1=7.2A{R}_{1} = 7 . 2A

Current in R2=x+y2=(7215−10815)12=12(3615)=2.42A{R}_{2} = \dfrac{x + y}{2} = \left(\dfrac{72}{15} - \dfrac{108}{15}\right)\dfrac{1}{2}= \dfrac{1}{2}\left(\dfrac{36}{15}\right) = \dfrac{2 . 4}{2}A

=1.2A= 1 . 2A

Current in R3=x=4.8A{R}_{3} = x = 4 . 8A

Current in R5=12x=2.4A{R}_{5} = \dfrac{1}{2}x = 2 . 4A

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