A potentiometer wire of length $1 \mathrm{m}$ is connected to a driver cell of emf $3 \mathrm{V}$ as shown in Fig. 

When a cell of $1.5 \mathrm{V} \mathrm{emf}$ is used in the secondary circuit, the balance point is found to be $60 \mathrm{cm}$. On replacing this cell and using a cell of unknown emf, the balance point shifts to $80 \mathrm{cm}$.

Does the high resistance $\mathrm{R}$, used in the secondary circuit affect the balance point? Justify your answer.

Figure shows the circuit diagram of a potentiometer for determining the emf $\text{'}\epsilon \text{'}$ of a cell of negligible internal resistance.

What is the purpose of using high resistance ${\mathrm{R}}_2$ ?

Figure shows the circuit diagram of a potentiometer for determining the emf $\text{'}\epsilon \text{'}$ of a cell of negligible internal resistance.

How does the position of balance point $\left(\mathrm{J}\right)$ change when the resistance ${\mathrm{R}}_1$ is increased?

Figure shows the circuit diagram of a potentiometer for determining the emf $\text{'}\epsilon \text{'}$ of a cell of negligible internal resistance.

Why cannot the balance point be obtained,
(a) when the emf E is greater than $2\mathrm{V}$, and
(b) when the key $\mathrm{K}$ is closed?

For the circuit shown in Figure , would the balancing length increase, decrease or remain the same, if (i) ${\mathrm{R}}_1$ is decreased, (in each case) in the rest of the circuit? Justify your answer in each case.

For the circuit shown in Figure , would the balancing length increase, decrease or remain the same, if ${\mathrm{R}}_2$ is increased without any other change, (in each case) in the rest of the circuit? Justify your answer in each case.

A potentiometer circuit is set up as shown in Fig. . The potential gradient across the potentiometer wire is $0.025 \mathrm{V}/\mathrm{cm}$ and the ammeter present in the circuit reads $0.1 \mathrm{A}$, when the two way key is completely switched off. The balance points, when the key between the terminals (i) 1 and 2 (ii) 1 and 3, is plugged in, are found to be at lengths $40 \mathrm{cm}$ and $100 \mathrm{cm}$ respectively. Find the values of $\mathrm{R}$ and $\mathrm{X}.$

The circuit diagram shows the use of a potentiometer to measure a small emf produced by a thermocouple connected between $\mathrm{X}$ and $\mathrm{Y}$. The cell C, of emf $2 \mathrm{V}$, has negligible internal resistance. The potentiometer wire $\mathrm{PQ}$ is $1.00$ m long and has resistance $5\mathrm{\Omega }$. The balance point $\mathrm{S}$ is found to be $400 \mathrm{mm}$ from $\mathrm{P}$. Calculate the value of emf generated by the thermocouple.

A resistance of $\mathrm{R\Omega }$ draws current from a potentiometer. The potentiometer has a total resistance of ${\mathrm{R}}_0\mathrm{\Omega }$ (Fig. 3.303). A voltage $\mathrm{V}$ is supplied to the potentiometer. Derive an expression for the voltage across $\mathrm{R}$ when the sliding contact is in the middle of the potentiometer.