The 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 W, the null point on it is found to be at 1000 cm. The resistance of whole wire is:

Question:

The length of a potentiometer wire is $1200 \mathrm{~cm}$ and it carries a current of $60 \mathrm{~mA}$. For a cell of emf $5 \mathrm{~V}$ and internal resistance of $20 \Omega$, the null point on it is found to be at $1000 \mathrm{~cm}$. The resistance of whole wire is:

  1. $80 \Omega$

  2. $120 \Omega$

  3. $60 \Omega$

  4. $100 \Omega$


Correct Option: 4

Solution:

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