Question 11.C-A.66: A graph of vacuum diode current I, is plotted against the an...
A graph of vacuum diode current I, is plotted against the anode voltage, V_{P} for two different temperatures T_{1} and T_{2} (T_{2} > T_{1}) of the cathode, as shown in the figure below.
(1) For the same anode voltage, (called plate voltage) why is the current more when the cathode temperature changes from T_{1} to T_{2}?
(2) In the part CD of the graph, why change in V_{p} has no effect on I_{P}?
(3) What is the plate current when plate voltage is zero? At what plate voltage the plate current is zero?
(i) As the temperature of the cathode increases, it starts emitting more and more number of electrons per second which on reaching the anode increases the plate current.
(ii) As the plate potential is increased, the plate current increases but it remains constant when the rate at which electrons are emitted from the cathode equals the rate at which they reach the anode.