Question

The plate current in a triode valve is zero. The temperature of the filament is high. It is possible that
(a) Vg > 0, Vp > 0
(b) Vg > 0, Vp < 0
(c) Vg < 0, Vp > 0
(d) Vg < 0, Vp < 0

Answer 1

Answer:

Here Vg means voltage grid and Vp means positive plate’s voltage. Now it is already given in question that temperature of the filament is high therefore electrons have enough kinetic energy to leave the surface of cathode.

But still even if grid voltage is negative, electrons will not able to reach the surface of anode and hence no current will be visible Also if positive plate’s voltage is negative, then also electrons won’t be able to reach the anode’s surface. Therefore, current will be zero even if one of the above conditions are met.