• # question_answer A triode valve has an amplification factor of 20 and its plate is given a potential of 300 V. The grid-voltage to reduce the plate current to   zero, is : A)  25V           B)  15V C)  12V            D)  10 V

The grid potential required to make plate current zero is given by ${{V}_{g}}=\frac{{{V}_{p}}}{\mu }$ Given, ${{V}_{p}}=300\,V,\,\mu =20$ $\therefore$ ${{V}_{g}}=\frac{300}{20}=15\,V$