The figure shows a network of four resistances and three batteries. The current through the branch $CF$ is ............... $A$.

What is a Wheatstone bridge? Explain its principle.

The Wheatstone bridge shown in the figure gets balanced when the carbon resistor used as $R_1$ has the colour code (Orange,Red,Brown). The resistors $R_2$ and $R_4$ are $80 \, \Omega$ and $40 \, \Omega$,respectively. Assuming that the colour code for the carbon resistors gives their accurate values,the colour code for the carbon resistor used as $R_3$ would be

In the balanced condition,the values of the resistances of the four arms of a Wheatstone bridge are shown in the figure below. The resistance $R_3$ has a temperature coefficient of $0.0004 \ {}^{\circ}C^{-1}$. If the temperature of $R_3$ is increased by $100 \ {}^{\circ}C$,the voltage developed between $S$ and $T$ will be. . . . . . . volt.

The potential difference $V$ across the filament of the bulb shown in the given Wheatstone bridge varies as $V = i(2i + 1)$,where $i$ is the current in ampere through the filament of the bulb. The emf of the battery $(V_b)$ so that the bridge becomes balanced is (in $V$)

$A$ $6 \, V$ cell with $0.5 \, \Omega$ internal resistance, a $10 \, V$ cell with $1 \, \Omega$ internal resistance, and a $12 \, \Omega$ external resistance are connected in parallel. The current (in ampere) through the $10 \, V$ cell is