If a $30\, V$, $90\, W$ bulb is to be worked on a $120\, V$ line, a resistance of how many ohms should be connected in series with the bulb ............... $ohm$

There are two electric bulbs of $40\, W$ and $100\, W$. Which one will be brighter when first connected in series and then in parallel,

Assertion : Long distance power transmission is done at high voltage.

Reason : At high voltage supply power losses are less.

A heating coil can heat the water of a vessel from $20\,^oC$ to $60\,^oC$ in $30$ minutes. Two such heating coils are put in series and then used to heat the same amount of water through the same temperature range. The time taken now will be ............ $min$ (neglecting thermal capacity of the coils)

The three resistance of equal value are arranged in the different combinations shown below. Arrange them in increasing order of power dissipation.

The resistance of hot tungsten filament is about $10$ times the cold resistance. What will be the resistance of $100\, W$ and $200\, V$ lamp when not in use ............. $\Omega $