Q. 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
A) 6.25 $V$
B) 0.16 $V$
C) 15.2 $V$
D) None of these
Explanation
(a) The first data gives value of plate resistance
$r_{p} = \frac{\Delta V_{p}}{\Delta i_{p}} = \frac{10}{0.8 \times 10^{- 3}} = \frac{10^{5}}{8}\Omega$
Also $g_{m} = \frac{\Delta i_{p}}{\Delta V_{g}}\ $and $g_{m} = \frac{\mu}{r_{p}}$
$\Rightarrow \Delta V_{g} = \frac{\Delta i_{p} \times r_{p}}{\mu} = \frac{4 \times 10^{- 3} \times 10^{5}/8}{8} = 6.25\ V$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.