CBSE-XI-Physics
41: Electric Current through Gases
- #4The saturation current in a triode valve can be changed by changing
(a) the grid voltage
(b) the plate voltage
(c) the separation between the grid and the cathode
(d) the temperature of the cathodedigAnsr: aAns : (a) the grid voltage
Since the triode value consists of a space charge region near the cathode, this space charge region is affected by the grid voltage. If the grid voltage is made negative, it repels the electrons coming from the cathode and reduces current. If this voltage is made positive, it helps the electrons move towards the anode. Hence, this voltage is more effective in changing the plate current. Since, the saturated current in the triode is the maximum value of plate current, the saturated current in the triode valve is effectively controlled by the grid voltage. More negative is the grid voltage, less is the value of saturated current.
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