The resistivity does not change if

$B_1, B_2$ and $B_3$ are three identical bulbs connected as shown in Figure. When all the three bulbs glow, a current of $3\,A$ is recorded by the ammeter $A$.

$(i)$ What happens to the glow of the other two bulbs when the bulb $B_1$ gets fused?

$(ii)$ What happens to the reading of $A_1, A_2, A_3$ and $A$ when the bulb $B_2$ gets fused?

$(iii)$ How much power is dissipated in the circuit when all the three bulbs glow together?

Two bulbs $A$ and $B$ are rated as $90\, W -120 \,V$ and $60\, W -120\, V$ respectively. They are connected in parallel across a $120\, V$ source. Find the current in each bulb. Which bulb will consume more energy ?

How much current will an electric bulb of resistance $1100\, \Omega$ draw from a $220\, V$ source $?$ If $a$ heater of resistance $100\, \Omega$ is connected to the same source instead of the bulb, calculate the current drawn by the heater.

If resistors are connected in parallel, the voltage across each remains the same.

Write Joule's law of heating.