Question

The dynamic plate resistance of a triode value is 10 kΩ. Find the change in the plate current if the plate voltage is changed from 200 V to 220 V.

Answer 1

Given:
Plate resistance, $r_{\mathrm{p}}\mathit{}=10\mathrm{K\Omega }={10}^4\mathrm{\Omega }$
Change in plate voltage, $\delta V_{\mathrm{p}}=220-200=20\mathrm{V}$
Plate resistance at constant grid voltage is given as:

$$\begin{gathered} r_{\mathrm{P}}=(\frac{\delta V_{\mathrm{P}}}{\delta I_{\mathrm{P}}}{)}_{V_{\mathrm{G}}=C\mathrm{onstant}} \\ \Rightarrow \delta I_{\mathrm{P}}=\frac{\delta V_{\mathrm{P}}}{r_{\mathrm{P}}} \\ \delta I_{\mathrm{P}}=\frac{\delta V_{\mathrm{p}}}{r_{\mathrm{P}}} \\ \delta I_{\mathrm{P}}=\frac{20}{{10}^4}=0.002\mathrm{A}=2\mathrm{mA} \end{gathered}$$