Exercises

To find the resistance of a gold bangle, two diametrically opposite points of the bangle are connected to the two terminals of the left gap of a metre bridge. A resistance of $4\Omega$ is introduced in the right gap. What is the resistance of the bangle if the null point is at $20 \mathrm{cm}$ from the left end?

Difference between potentiometer and voltmeter

What will be the effect on the position of zero deflection if only the current flowing through the potentiometer wire is decreased?

 A potentiometer wire has a length of $1.5 \mathrm{m}$ and resistance of $10 \mathrm{\Omega }$. It is connected in series with the cell of emf $4 \mathrm{Volt}$ and internal resistance $5\mathrm{\Omega }$ Calculate the potential drop per centimeter of the wire.

When two cells of emfs.${\epsilon }_1$and ${\epsilon }_2$ are connected in series so as to assist each other, their balancing length on a potentiometer is found to be $2.7 \mathrm{m}$. When the cells are connected in series so as to oppose each other, the balancing length is found to be $0.3$ in. Compare the emfs of the two cells.

The emf of a cell is balanced by a length of $120 \mathrm{cm}$ of potentiometer wire. When the cell is shunted by a resistance of $10\mathrm{\Omega }$, the balancing length is reduced by $20 \mathrm{cm}$. Find the internal resistance of the cell. 

A potential drop per unit length along a wire is $5\times {10}^{-3}\mathrm{V}/\mathrm{m}$. If the emf of a cell balances against length $216 \mathrm{cm}$ of this potentiometer wire, find the emf of the cell. 

 Find the equivalent resistance between the terminals F and B in the network shown in the figure below given that the resistance of each resistor is $10 \mathrm{ohm}$.