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  • Solve this problem - An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potent - Current Electricity - JEE Main

 An ideal battery of 4 V and resistance R are connected in series in the primary circuit of a potentiometer of length 1 m and resistance 5 \Omega . The value of R , to give a potential difference of 5mV across 10 cm of potentiometer wire , is : 

 

  • Option 1)

     395 \Omega 

  • Option 2)

     490 \Omega

  • Option 3)

    480 \Omega

  • Option 4)

     495 \Omega

Answers (1)

best_answer

 

Potential gradient -

Potential difference per unit length of wire    

- wherein

x=\frac{V}{L}

    R_{AB}=5-2\, \, \, \, \, L_{AB}=1m

 

i=\frac{v}{R+5}=\frac{4}{R+5}A

for 1m resistance is 5\Omega

so for 10 cm

R_{10cm}=5\times \frac{10}{100}=0.5\Omega

\Delta v_{10cm}=i.R_{10.cm}

5\times 10^{-3}=\left ( \frac{4}{R+5} \right )\times 0.5

\frac{4}{R+5}=10\Omega

R+5=400\Omega

R=395\Omega

 

 


Option 1)

 395 \Omega 

Option 2)

 490 \Omega

Option 3)

480 \Omega

Option 4)

 495 \Omega

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