$A$ uniform wire of $16\,\Omega$ is bent into the form of a square. Two opposite corners of the square are connected by a wire of resistance $16\,\Omega$. The effective resistance between the other two opposite corners is ............... $\Omega$.

In a Wheatstone bridge (see figure),resistances $P$ and $Q$ are approximately equal. When $R = 400 \,\Omega$,the bridge is balanced. On interchanging $P$ and $Q$,the value of $R$ for balance is $405 \,\Omega$. The value of $X$ is close to ................. $\Omega$. (in $.5$)

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.

Kirchhoff's first law,$i.e.$,$\Sigma i = 0$ at a junction,is based on the law of conservation of:

The value of current through the $20\,\Omega$ resistor is .................. $A$.

The potential difference between $A$ and $B$ in the following figure is (in $V$)