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Need explanation for: - Current Electricity - JEE Main-3

In the circuit shown, a four-wire potentiometer is made of a 400 cm long wire, which extends between A and B. The resistance per unit length of the potentiometer wire is r=0.01\;\Omega /cm. if an ideal voltmeter is connected as shown with jockey J at 50 cm from end A, the expected reading of the voltlmeter will be:

  • Option 1)

    0.50 V

  • Option 2)

    0.75 V

  • Option 3)

    0.25 V

  • Option 4)

    0.20 V

 
Answers (1)
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I=\frac{1.5+1.5}{1+1+R_{AB}}

R_{AB}=400 \times 0.01=4 \Omega

I=\frac{3}{6}=\frac{1}{2}=0.5A

Volmeter \;Reading=I \times R_{50 cm}

V=\left ( 0.5 \right )\times \left ( 0.01 \times 50 \right )

V=0.25 \;volt


Option 1)

0.50 V

Option 2)

0.75 V

Option 3)

0.25 V

Option 4)

0.20 V

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