In the circuit shown in the figure,if the potential at point $A$ is taken to be zero,the potential at point $B$ is ................ $V$.

$A$ $50\, W$ bulb is in series with a room heater and the combination is connected across the mains. To get maximum heater output,the $50\, W$ bulb should be replaced by a bulb of: (in $, W$)

If the ammeter in the given circuit reads $2\, A$,the resistance $R$ is ............ $\Omega$.

Two voltameters,one of copper and another of silver,are joined in parallel. When a total charge $q$ flows through the voltameters,equal amounts of metals are deposited. If the electrochemical equivalents of copper and silver are $z_1$ and $z_2$ respectively,the charge which flows through the silver voltameter is

The emf of a cell of internal resistance $2 \ \Omega$ is measured using a voltmeter of resistance $998 \ \Omega$. The error in the emf measured is (in $\%$)

$A$ uniform metallic wire carries a current of $2\,A$ when a $3.4\,V$ battery is connected across it. The mass of the uniform metallic wire is $8.92 \times 10^{-3}\,kg$,its density is $8.92 \times 10^3\,kg/m^3$,and its resistivity is $1.7 \times 10^{-8}\,\Omega\cdot m$. The length of the wire is $l = \dots\dots\dots\dots\,m$.