Question

The amplification factor of a triode valve is $15$. If the grid voltage is changed by $0.3\,V$, the change in plate voltage in order to keep the current constant (in volt) is:

• A. 0.02
• B. 0.002
• C. 4.5
• D. 5.0

Answer 1

Answer: (C)

The ratio of the decrease in plate potential (while grid potential is kept constant) to the increase in grid potential (while plate potential is kept constant) for a definite increase in the plate current is called the amplification factor of the triode valve.
$ \mu =\frac{\Delta {{V}_{p}}}{\Delta {{V}_{g}}} $
Given, $ \mu =15,\,\Delta {{V}_{g}}=0.3\,V, $
$ \Rightarrow $ $ \,\Delta {{V}_{p}}=\mu \times \,{{V}_{g}} $
$ \,\Delta {{V}_{p}}=15\times 0.3 $
$ \,\Delta {{V}_{p}}=4.5\,V $
$ \mu $ has no unit and its value is always greater than one.