In a potentiometer experiment, it is found that no current passes through the galvanometer when the terminals of the cell are connected across $52\mathrm{cm}$ of the potentiometer wire. If the cell is shunted by resistance of $5 \mathrm{\Omega }$, a balance is found when the cell is connected across $40 \mathrm{cm}$ of the wire. Find the internal resistance of the cell.

A D.C. supply of $120$ volt is connected to a large resistance $\mathrm{X}$. A volt meter of resistance $10 \mathrm{k\Omega }$, placed in series in the circuit reads $4$ volts. What is the value of $\mathrm{X}$? What do you think is the purpose in using a voltmeter, instead of an ammeter, to determine the large resistance $\mathrm{X}$?

A cell of emf$3.4$ volt and internal resistance $3\mathrm{\Omega }$ connected to an ammeter having resistance $2\mathrm{\Omega }$ and to an external resistance of$100\mathrm{\Omega }$. When a voltmeter is connected across the $100 \mathrm{\Omega }$ resistance the ammeter reading is $0.04$ ampere. Find the voltage read by the voltmeter and its resistance. Had the voltmeter been an ideal one, what would have been its reading.

(Approximate the answer to two decimal places)

In the circuit shown in figure, all wires have equal resistance $\mathrm{r}$. Calculate equivalent resistance between $\mathrm{A}$ and $\mathrm{B}$?