In a potentiometer of one metre length, an unknown emf voltage source is balanced at `60 cm` length of potentiometer wire, while a `3` volt battery is balanced at `45 cm` length. The the emf of the unknown voltage source is.

Options

A. 3 V
B. 2.25 V
C. 4 V
D. 4.5 V

Answer

C

Explanation

`(E_1)/(l_1) = (E_2)/(l_2)`
`(E_1)/(60) = (3)/(45) rArr E_1 = 4 V`.