Question

A body has a positive charge of $8 \times {10^{ - 19}}C$. It has:
A) An excess of 5 electrons
B) A deficiency of 5 electrons
C) An excess of 8 electrons
D) A deficiency of 8 electrons

Answer 1

Hint: In this question, the body has positive charge. The positive charge on the body means the decrease in the number of electrons and an increase in the number of protons. The value of charge on electrons and on protons is equal. They are different in their signs. Electrons are a negative charge and protons are a positive charge.

Formula used:
Deficiency of electrons = $\dfrac{\text{Positive charge on the body}}{{\text{Charge of an electron}}}$

Complete step by step solution:
We know that the positive charge on a body indicates that the body has a deficiency of negative charge i.e. deficiency of electrons in the body. A body is said to be neutral if the number of electrons and protons are equal in the body. If the body has a deficiency of electrons, then the body has a positive charge. In contrast, if a body has a deficiency of protons then the body has a negative charge.
In this way, it is clear that the body has a deficiency of electrons.
Let us find the number of electrons. The number of electrons is the ratio of positive charge on the body and charge of an electron. So,
Deficiency of electrons = $\dfrac{\text{Positive charge on the body}}{{\text{Charge of an electron}}}$
$ \Rightarrow \text{Deficiency of electrons} = \dfrac{{{\text{8}} \times {\text{1}}{{\text{0}}^{{\text{ - 19}}}}}}{{{\text{1}}{\text{.6}} \times {{10}^{ - 19}}}} \\
\Rightarrow \text{Deficiency of electrons} = \dfrac{{80}}{{16}} \\
\Rightarrow \text{Deficiency of electrons} = 5 \\ $
Hence, the body has a deficiency of $5$ electrons. Therefore, option (B) is correct.

Note:
A body is always said to be neutral in general. if the body has any type of charge then the body has a deficiency of opposite charge. If a body has a negative charge, then the body has a deficiency of protons. In other words, the body has an excess of electrons.