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# In experiment of the potentiometer wire AB of length 100 cm has a resistance of 10Ω, It is connected in series with a resistance R and a cell of emf 2 volts and of negligible internal resistance.A Source of emf 10mV is balanced against a length of of 40 cm the poteatio meter wire. What is the value of the external resistance?

- 900Ω
- 820Ω
- 790Ω
- 670Ω

## The correct answer is: 790Ω

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