What are the essential requirements of a heater filament?

What is the equivalent resistance of a circuit when three resistors of $5 \Omega$,$10 \Omega$,and $30 \Omega$ are connected in parallel (in $\Omega$)?

What is the resistance of an ideal ammeter?

In an electrical circuit,two resistors of $2\,\Omega$ and $4\,\Omega$ respectively are connected in series to a $6\,V$ battery. The heat dissipated by the $4\,\Omega$ resistor in $5\,s$ will be ........ $J$.

The equivalent resistance between points $A$ and $B$ of the following electric circuit will be $.........$

What is the maximum resistance which can be made using five resistors each of $1/5 \ \Omega$ (in $\Omega$)?