A potentiometer is supplied a constant voltage of 5 V. A cell of emf 1.4 V is balanced by the voltage drop across 280 cm of the potentiometer wire. The total length of the potentiometer wire will be:
Answer & explanation
Correct answer: option 3
Let Potential drop per unit length across potentiometer wire is V .
Since 1.4V is balanced by 280cm = 2.8 m.
$\Rightarrow V = \frac{1.4}{2.8} = 0.5 V/m$
Length required to balance 5V potential difference is $ L = \frac{5}{0.5}= 10m$