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?

A series combination of a $2 \mathrm{k\Omega }$ resistor and $1 \mathrm{k\Omega }$ resistor, is connected across a battery of emf $6 \mathrm{V}$ and

negligible internal resistance. The potential drop, across the $2 \mathrm{k\Omega }$ resistor, is measured by (i) a $30 \mathrm{k\Omega }$ voltmeter (ii) a $1 \mathrm{k\Omega }$ voltmeter and (iii) both these voltmeters connected across it, as shown in Fig. . If the voltmeter readings in the three cases are ${\mathrm{V}}_1, {\mathrm{V}}_2$ and ${\mathrm{V}}_3$ respectively, arrange these readings in descending order.

How will the three readings compare with one another if the potential drops were measured across the series combination of the $2 \mathrm{k\Omega }$ and the $1 \mathrm{k\Omega }$ resistor i.e., across the series combination of the $2 \mathrm{k\Omega }$ and the $1 \mathrm{k\Omega }$ resistor i.e., across the points $\mathrm{A}$ and $\mathrm{B}$ ?

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 shown in the Fig. contains a battery $\text{'}\mathrm{B}\text{'}$, a rheostat $\text{'}\mathrm{Rh}\text{'}$ and identical lamps $\mathrm{P}$ and $\mathrm{Q}$.What will happen to the brightness of the lamps, if the resistance through the rheostat is increased? Give reasons.

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.