In a copper voltameter,the mass deposited in $30\, \text{s}$ is $m\, \text{g}$. If the current-time graph is as shown in the figure,the Electrochemical Equivalent $(ECE)$ of copper is:

If the resistance of each edge of a cube-shaped wire frame as shown in the figure below is $R$,then the resistance between points $1$ and $7$ is

The potential difference $V_B - V_A$ in the network shown is ............. $V$.

An electric bulb rated for $500\, W$ at $100\, V$ is used in a circuit having a $200\, V$ supply. The resistance $R$ that must be put in series with the bulb,so that the bulb draws $500\, W$,is ................. $\Omega$.

The emf of a thermocouple,one junction of which is kept at $0\,^{\circ}C$,is given by $e = at + bt^2$. The Peltier coefficient will be

The series combination of two batteries,both of the same emf $10 \; V,$ but different internal resistances of $20 \; \Omega$ and $5 \; \Omega,$ is connected to the parallel combination of two resistors $30 \; \Omega$ and $R \; \Omega.$ If the voltage difference across the battery of internal resistance $20 \; \Omega$ is zero,the value of $R$ (in $\Omega$) is: