What is the unit of $Watt-second$?

What are the essential requirements of a heater filament?

What is the resistance of an electric arc lamp,if the lamp uses $20\, A$ when connected to a $220\, V$ line?

How will you infer with the help of an experiment that the same current flows through every part of the circuit containing three resistances in series connected to a battery?

Name the commercial unit of electrical energy. Convert it into joule. What is the other name of the commercial unit?

State with the help of a circuit diagram an activity to find the resistance $R$ of a given wire. $A$ current of $0.2 \, A$ passes through a resistor of $20 \, \Omega$. Find the potential difference across its ends.