Which of the following has the unit $volt$?

There is a frill of $20$ bulbs connected in series in a room. One bulb gets fused. The remaining $19$ are again joined in series and connected to the same supply. Will the light increase or decrease in the room?

Which alloy is used to make the heating element (resistance wire) in an electric iron?

Why are alloys commonly used in electrical heating devices?

Mention the condition under which charges can move in a conductor. Name the device which is used to maintain this condition in an electric circuit.

What is electrical resistivity? In a series electrical circuit comprising a resistor made up of a metallic wire, the ammeter reads $5\, A$. The reading of the ammeter decreases to half when the length of the wire is doubled. Why?