Q. In a potentiometer of one metre length, an unknown $e.m.f.$ voltage source is balanced at 60 cm length of potentiometer wire, while a 3 volt battery is balanced at 45 cm length. Then the $e.m.f.$ of the unknown voltage source is
A) $3V$
B) $2.25V$
C) $4V$
D) $4.5V$
Explanation
(c) $E_{1} = ?,\ l_{1} = 60cm;E_{2} = 3V,\ l_{2} = 45cm$
In balance condition
$\frac{E_{1}}{E_{2}} = \frac{l_{1}}{l_{2}} \Rightarrow \frac{E_{1}}{3} = \frac{60}{45} \Rightarrow E_{1} = 4\ volt$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.