Draw a schematic diagram of an electric circuit consisting of a battery of two cells each of $1.5\, V$, $5\, \Omega, 10\, \Omega$ and $15\, \Omega$ resistors and a plug key, all connected in series.

What are the units of resistance ?

$(a)$ 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 $10^{10}-10^{\text {14 }} \;\Omega m$ 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?

The amount of charge passing through a cell in four second is $12 \,C .$ Find the current supplied by cell.

An electric iron has a rating of $750\, W ; 200\, V$. Calculate

$(i)$ the current required.

$(ii)$ the resistance of its heating element.

$(iii)$ energy consumed by the iron in $2$ hours.

An electric bulb draws a current of $0.2 A$ when the voltage is $220$ volts. Calculate the amount of charge flowing through it in one hour.