Which of the following does not vary with plate or grid voltages in a vacuum triode?

In the space charge limited region,the plate current in a diode is $10\, mA$ for a plate voltage of $150\, V$. If the plate voltage is increased to $600\, V$,then the plate current will be.......$mA$.

The amplification factor of a triode is $10$. When the plate potential is $200 \, V$ and the grid potential is $-4 \, V$,a plate current of $4 \, mA$ is observed. If the plate potential is changed to $160 \, V$ and the grid potential is kept at $-7 \, V$,then the plate current will be.....$mA$.

On applying a potential of $-1 \ V$ at the grid of a triode,the following relation between plate voltage $V_p$ $(V)$ and plate current $I_p$ (in $mA$) is found:
$I_p = 0.125 V_p - 7.5$
If on applying $-3 \ V$ potential at the grid and $300 \ V$ potential at the plate,the plate current is found to be $5 \ mA$,then the amplification factor of the triode is:

For a triode,at ${V_g} = -1 \text{ V}$,the following observations were taken: ${V_p} = 75 \text{ V}, {I_p} = 2 \text{ mA}$ and ${V_p} = 100 \text{ V}, {I_p} = 4 \text{ mA}$. The value of plate resistance will be ...... $k\Omega$.

In a triode valve,the amplification factor is $20$ and the mutual conductance is $10^{-3} \text{ mho}$. The plate resistance is: