What are the advantage and disadvantage of semiconductor devices over vacuum tubes?

The space charge limited current in a diode is $16 \mathrm{mA}$ at $80 \mathrm{V}.$ At what voltage its value will be $128 \mathrm{mA}.$ (Write the numerical answer in terms of $\mathrm{V}$.)

What are the advantages of semiconductor diodes over vacuum diode?

Correct the following sentence:

The space charge limited current varies directly as the square root of plate current.

Represent the union of two sets by Venn diagram for each of the following.

$X=\{x | x$ is a prime number between $80$ and $100\}$

$Y=\{y | y$ is an odd number between $90$ and $100\}$

The space charge limited current in a diode is $2 \mathrm{mA}$ at $20 \mathrm{V}.$ At what voltage its value will be $16 \mathrm{mA}.$