Which instrument is used to measure electric current?

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?

When three resistors of $5 \Omega$,$10 \Omega$,and $30 \Omega$ are connected in parallel in a circuit,what will be the equivalent resistance?

How many electrons will there be in $1.6 \ C$ charge?

How will you conclude that the same potential difference (voltage) exists across three resistors connected in a parallel arrangement to a battery?

$(a)$ How much current will an electric bulb draw from a $220 \ V$ source,if the resistance of the bulb filament is $1200 \ \Omega$?
$(b)$ How much current will an electric heater coil draw from a $220 \ V$ source,if the resistance of the heater coil is $100 \ \Omega$?