If the resistance of a conductor is doubled,the current is halved.

Name and define the $SI$ unit of resistance. Calculate the resistance of a resistor if the current flowing through it is $200\, mA$, when the applied potential difference is $0.8\, V$.

Define one ampere.

Explain how do we classify materials as conductors and insulators on the basis of their resistance.

$(i)$ Draw a circuit diagram to show how two resistors are connected in series.
$(ii)$ In a circuit,if two resistors of $5 \ \Omega$ and $10 \ \Omega$ are connected in series,how does the current passing through the two resistors compare?

An electric bulb of resistance $480 \Omega$ is connected to a $220 \text{ V}$ main. Find the amount of electrical energy consumed in $10 \text{ seconds}$. (in $J$)