In an amplifier,the load resistance ${R_L}$ is equal to the plate resistance ${r_p}$. The voltage amplification is equal to:

If ${R_p} = 7 \text{ k}\Omega$ and ${g_m} = 2.5 \text{ millimho}$, then on increasing the plate voltage by $50 \text{ V}$, how much must the grid voltage be changed so that the plate current remains the same? (in $V$)

The value of the amplification factor from the following graph is:

The linear portions of the characteristic curves of a triode valve give the following readings. The plate resistance is ....... $\Omega$.

$V_g$ (volt)	$0$	$-2$	$-4$	$-6$
$I_p$ (mA) for $V_p = 150$ $V$	$15$	$12.5$	$10$	$7.5$
$I_p$ (mA) for $V_p = 120$ $V$	$10$	$7.5$	$5$	$2.5$

The voltage gain of a triode depends upon

Coating of strontium oxide on a tungsten cathode in a valve is good for thermionic emission because: