Question

In a vacuum diode, some of the electrons possessing sufficient kinetic energy can reach the plate even if the plate potential is negative. For a certain diode, the plate current becomes zero when plate potential is $-10V$. What is the kinetic energy of the electrons in $eV$, if the plate potential is $-4V$ ?

• A. $3eV$
• B. $6eV$
• C. $4eV$
• D. $-4eV$

Answer 1

The correct option is B $6eV$

$\begin{array}{cc}& \begin{array}{cc}K{E}_{max}& =e{V}_{min}\\ K{E}_{max}& =\mathrm{10e}V\end{array}\\ \text{KE, in this case}& =k{E}_{max}-eV\\ & \begin{array}{cc}=& \text{10ev}-4eV\\ =& 6eV\end{array}\end{array}$