The resistive network shown below is connected to a $D.C.$ source of $16 \, V$. The power consumed by the network is $4 \, W$. The value of $R$ is ............. $\Omega$.

The power dissipated in the circuit shown in the figure is $30 \, W$. The value of $R$ is ............. $\Omega$.

Resistance $n$,each of $r \ \Omega$,when connected in parallel give an equivalent resistance of $R \ \Omega$. If these resistances were connected in series,the combination would have a resistance in $\Omega$,equal to

$A$ copper wire of radius $r$ and length $\ell$ is coated with a nickel layer until its radius becomes $2r$. If the resistivities of copper and nickel are $\rho_c$ and $\rho_n$ respectively,find the equivalent resistance of the wire.

Four identical bulbs,each rated $100 \, W, 220 \, V$,are connected across a battery as shown. The total electric power consumed by the bulbs is.......$W$.

The equivalent resistance between $A$ and $B$ is $......$