What is the unit of resistance?

$A$ cell,a resistor,a key and an ammeter are arranged as shown in the circuit diagrams of the figure. The current recorded in the ammeter will be

$A$ wire connected to a bulb does not glow,whereas the filament of the bulb glows when the same current is passed through them. Why?

What is meant by resistance?

$A$ battery is a source of maintaining a constant potential difference across two ends of a conductor.

An electric iron draws a current of $0.5\, A$ when the voltage is $200\, V$. Calculate the amount of electric charge flowing through it in one hour. (in $C$)