Question

A gold coin has a charge of $+{{10}^{-4}}C$. The number of electrons removed from it is:
(A). ${{10}^{6}}$
(B). $625\times {{10}^{12}}$
(C). $1.6\times {{10}^{-25}}$
(D). $1.6\times {{10}^{13}}$

Answer 1

- Hint: To answer this question first find the charge for a single electron. Since electrons are negatively charged and we have a positively charged metal coin we need to remove electrons from the coin. Find the number of electrons by dividing the given charge with charge of a single electron.

Complete step-by-step solution -
Electrons are subatomic particles. The charge on an electron is given by, $e=-1.6\times {{10}^{-19}}C$. Electrons is a negatively charged particle.
In an element we have both protons and electrons. Protons and electrons both have the same amount of charge but both are oppositely charged. Protons are positively charged and electrons are negatively charged.
From an element we can only remove or add an electron. On the basis of this the element will be positively charged or negatively charged. If we add electrons to the element it will be negatively charged and if we add electrons, we will have a positively charged electron.
In the question we are given that the gold coin has a positive charge of $Q=+{{10}^{-4}}C$ .
Now, the number of electrons removed from the gold coin can be given as,
$\begin{align}
  & n=\dfrac{{{10}^{-4}}C}{1.6\times {{10}^{-19}}C} \\
 & n=625\times {{10}^{12}} \\
\end{align}$
The correct option is (B).

Note: Proton is a positively charged subatomic particle with charge $p=+1.6\times {{10}^{-19}}C$. We can make an atom positively charged by removing electrons from the atom and negatively charged by adding electrons from the atom. We cannot add or remove protons from an atom to change its charge. We can only add or remove electrons to change the charge of the atom or material.