JEE Main & Advanced Physics Current Electricity, Charging & Discharging Of Capacitors / वर्तमान बिजली, चार्ज और कैपेसिटर का निर JEE PYQ-Current Electricity Charging and Discharging of Capacitors

In a metre bridge experiment null point is obtained at 40 cm from end of the wire when resistance X is balanced against another resistance Y. if X < Y, then the new position of the null point from the same end, if one decides to balance a resistance of 3X against Y, will be close to: [JEE ONLINE 09-04-2013]

A) 80 cm

B) 75 cm

C) 67 cm

D) 50 cm

Correct Answer: C

Solution :

[c] As \[\frac{x}{y}=\frac{40}{100-40}=\frac{40}{60}\]

\[\frac{3x}{y}=3\left( \frac{40}{60} \right)=\frac{120}{60}=\frac{2}{1}\]

Now, the total length = 100

\[\therefore \] Required length \[=\frac{100}{3}\times 2=67\,m\].