Question

An alpha particle (a bare helium nucleus with $q=+2e$) acceler-ates across a $100V$ potential difference, starting from rest. What is the particle’s kinetic energy in eV when it reaches the negative electrode? This question requires no mathematics beyond what you can do in your head.

Short answer

The particle’s kinetic energy in eV when it reaches the negative electrode is $200eV$.

Step-by-step solution

Given information

We have given-

$$\begin{gathered} q=+2e \\ ∆V=0 \\ Ki=0 \end{gathered}$$

( As the body starts from rest )

Explanation

As we know,

Work done by all forces = Change in Kinetic Energy

so,

$$\begin{gathered} Wall=∆KE \\ Wp.d.=Kf-Ki \\ q∆V=Kf-0 \\ 2e\times 100V=Kf \\ 200eV=Kf \end{gathered}$$