A potentiometer wire of length 1000 cm has a resistance of 10 ohms. It is connected in series with a resistance and a cell of e.m.f 2 volts and of negligible internal resistance. A source of e.m.f 10 millivolts is balanced against a length of 40 cm of the potentiometer wire. What is the value of the external resistance?A. 1.5VB. 3.0VC. 0.67VD. 1.33V

A potentiometer wire of length 1000 cm has a resistance of 10 ohms. It

1.	A potentiometer wire of length 1000 cm has a resistance of 10 ohms. It is connected in series with a resistance and a cell of e.m.f 2 volts and of negligible internal resistance. A source of e.m.f 10 millivolts is balanced against a length of 40 cm of the potentiometer wire. What is the value of the external resistance?A. 1.5VB. 3.0VC. 0.67VD. 1.33V
Answer» Correct Answer - 2 `because E=((V)/(L))xxlrArrE=((IR_(W))/(LL))xxl` `rArr E=(E_(0))/(R+r+R_(W))xx(R_(W))/(L)xxl` `E=(10)/(4+1+5)xx(5)/(3)xx3=3` volt

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