Positive charges flow from high potential to low potential.

What is the practical unit used for electrical energy?

What is the process of depositing a layer of gold on silver called?

$(a)$ Resistivity of iron is $10 \times 10^{-8} \; \Omega m$ and of mercury is $94 \times 10^{-8} \; \Omega m$. Which among iron and mercury is a better conductor? Give reason.
$(b)$ Resistivity of a material $A$ is in the range of $10^{10}-10^{14} \; \Omega m$ while that of $B$ is in the range of $10^{-6}-10^{-8} \; \Omega m$. Which of the two will behave as an insulator and why?

$(a)$ Explain how a cell maintains current in a circuit.
$(b)$ In the circuit given below,the resistance of the path $xTy = 2 \, \Omega$ and that of $xZy = 6 \, \Omega$.
$(i)$ Find the equivalent resistance between $x$ and $y$.
$(ii)$ Find the current in the main circuit.
$(iii)$ Calculate the current that flows through the path $xTy$ and $xZy$.

$A$ $100 \text{ W}$ electric bulb is lighted for $2 \text{ hours}$ daily,and four $40 \text{ W}$ bulbs are lighted for $4 \text{ hours}$ everyday. Calculate the energy consumed (in $\text{kWh}$) in $30 \text{ days}$.