Question

Draw the force that Q feels as a bold arrow pointing from the charge. Q= 5 coulombs x = 2 meters V=100 volts across the plates. For the parallel plate arrangement, the voltage and electric field are related by the spacing between the plates like this : V= Ex. How much energy is that in Joules? Remember that energies expressed in electron volts are: 1 eV= 1.6 x 10^-19 J. What is the energy of each electron in electron volts?

Answer 1

The charge is given as,

$Q=5\text{ C}$

The potential difference is given as,

$V=100\text{ V}$

The potential difference is defined as the work done per unit charge. Mathematically,

$V=\frac{W}{Q}$

Here, W is the work done that is stored in the form of energy. Therefore,

$W=VQ$

Substituting all known values,

$\begin{gathered} W=(100\text{ V})\times(5\text{ C}) \\ =500\text{ J} \end{gathered}$

Therefore, the energy is 500 J.

The energy of each electron placed between the charged plates is given as,

$W=qV$

Here, q is the charge on the electron.

Substituting all known values,

$\begin{gathered} W=(1.6\times10^{-19}\text{C})\times(100\text{ V}) \\ =1.6\times10^{-17}\text{ J} \end{gathered}$

Since we know that 1 eV equals 1.6*10^(-19) J.

Therefore, the energy of each electron in eV is given as,

$\begin{gathered} W=(1.6\times10^{-17}\text{ J})\times(\frac{1\text{ eV}}{1.6\times10^{-19}\text{ J}}) \\ =100\text{ eV} \end{gathered}$

Therefore, the energy of each electron is 100 eV.