Question 856: Electrostats & Capacitance

Question

An electron moving with velocity $$1.6 	imes 10^7 \mathrm{~m} / \mathrm{s}$$ has wavelength of $$0.4 \mathop A\limits^o$$. The required accelerating voltage for the electron motion is [charge on electron $$=1.6 	imes 10^{-19} \mathrm{C}$$, mass of electron $$=9 	imes 10^{-31} \mathrm{~kg}$$ ]

Accepted Answer

When an electron is accelerated through a voltage its kinetic energy is converted into electric potential energy:
$$\begin{aligned}
& \mathrm{K}=\mathrm{U} \
& \frac{1}{2} \mathrm{mv}^2=\mathrm{eV} \
	herefore \quad \mathrm{V} & =\frac{\mathrm{mv}^2}{2 \mathrm{e}} \
& \mathrm{V}=\frac{\left(9 	imes 10^{-31}ight)\left(1.6 	imes 10^7ight)^2}{2 	imes 1.6 	imes 10^{-19}}=7.2 	imes 10^2 \mathrm{~V}
\end{aligned}$$

Answer

$$7.2 	imes 10^3 \mathrm{~V}$$

Answer

$$7.2 	imes 10^2 \mathrm{~V}$$

Answer

$$7.2 \mathrm{~V}$$

Answer

$$7.2 	imes 10^{-2} \mathrm{~V}$$

Electrostats & Capacitance

An electron moving with velocity $1.6 \times 10^7 \mathrm{~m} / \mathrm{s} has wavelength of 0.4 \mathop A\limits^o. The required accelerating voltage for the electron motion is [charge on electron =1.6 \times 10^{-19} \mathrm{C}, mass of electron =9 \times 10^{-31} \mathrm{~kg}$ ]

Choose the correct answer: