In the circuit shown in the figure, a voltmeter reads $30 \mathrm{V}$ when it is connected across the $400 \mathrm{\Omega }$ resistance. Calculate what the same voltmeter will read when it is connected across the $300 \mathrm{\Omega }$ resistance.

The galvanometer in each of the two given circuits, Figure does not show any deflection. Find the ratio of resistors ${\mathrm{R}}_1$ and ${\mathrm{R}}_2$ used in their circuits.

Calculate the value of $\mathrm{R}$ in the balance condition of the Wheatstone bridge, if the carbon resistor connected across the arm $\mathrm{C} \mathrm{D}$ has the colour sequence red, red and orange as shown in the figure, Fig. If now the resistance of the arms $\mathrm{B} \mathrm{C}$ and $\mathrm{C} \mathrm{D}$ are interchanged, to obtain the balance condition, another carbon resistor is connected in place of $\mathrm{R}$. What now be the sequence of colour bands of the carbon resistor?

Two cells of emfs ${\mathrm{ϵ}}_1$ and ${\in }_2\left({\mathrm{ϵ}}_1>{\mathrm{ϵ}}_2\right)$ are connected as shown in Fig. When a potentiometer is connected between $\mathrm{A}$ and $\mathrm{B}$, the balancing length of the potentiometer wire is $3.00 \mathrm{m}$. on connecting the same potentiometer between $\mathrm{A}$ and $\mathrm{C},$ the balancing length is $1.00 \mathrm{m}.$ Calculate the ratio of ${\mathrm{ϵ}}_1$ and ${\mathrm{ϵ}}_2$. 

In the circuit shown in Fig. each battery is $5 \mathrm{V}$ and has an internal resistance of $0.2 \mathrm{\Omega }$. What is the reading in the ideal voltmeter?

In the circuit shown in Fig. the resistances $\mathrm{P}$ and $\mathrm{R}$ are unequal. If the reading of the galvanometer remains the same with the switch $\mathrm{S}$ open or closed, then what is the value of current through the galvanometer?

For the circuit shown in Fig. would the balancing length increase, decrease or remain the same, if  ${\mathrm{R}}_1$ is decreased

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

Reading on a high resistance voltmeter, when a cell is connected across it, is $2.5 \mathrm{V}$. When the terminals of the cell are also connected to a resistance $5 \mathrm{\Omega }$ as shown in circuit of Fig.  the voltmeter reading drops to $2.0 \mathrm{V}$. Find the internal resistance of the cell.