When a certain potentiometer is used to measure an unknown emf, the standard emf has a value of `1.2076 V`. When the standard emf is in the circuit and resistances `R_1` and `R_2` are adjusted so that no current flows through the galvanometer, the values of `R_1` and `R_2` are `2.42 Omega` and `4.84 Omega`, respectively. When the unknown emf is in the circuit, the value of `R_2` is `3.66 Omega`. What is the value of the unknown emf ?

Explanation

`R_1 + R_2 = R'_1 + R'_2`
`2.42 + 4.84 =R'_1 + 3.66`
`R'_1 = 3.6 Omega`
`(E_1)/(R_1) = (E_2)/(R'_1)`
`(1.2076)/(2.42) = (E_2)/(3.6)`
`E_2 = 1.8 V`.