The correct relation for a triode is

In the circuit of a triode valve,there is no change in the plate current when the plate potential is increased from $200 \ V$ to $220 \ V$ and the grid potential is decreased from $-0.5 \ V$ to $-1.3 \ V$. The amplification factor of this valve is

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:

With a change of load resistance of a triode, used as an amplifier, from $50 \, k\Omega$ to $100 \, k\Omega$, its voltage amplification changes from $25$ to $30$. The plate resistance of the triode is.....$k\Omega$.

$A$ change of $0.8 \,mA$ in the anode current of a triode occurs when the anode potential is changed by $10 \,V$. If $\mu = 8$ for the triode,then what change in the grid voltage would be required to produce a change of $4 \,mA$ in the anode current?

How many electrodes are in the tetrode?