What are the essential requirements of a heater filament?

$A$ 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

An electric bulb works on the heating effect of current.

$1 \; kWh = \ldots \ldots \; \text{joules}$

$1 \; kWh = \ldots \ldots \ldots \; \text{watt-seconds}$

Draw a circuit diagram of an electric circuit containing a cell,a key,an ammeter,a resistor of $2\,\Omega$ in series with a combination of two resistors ($4\,\Omega$ each) in parallel and a voltmeter across the parallel combination. Will the potential difference across the $2\,\Omega$ resistor be the same as that across the parallel combination of $4\,\Omega$ resistors? Give reason.