Question

The quantum of electric charge in e.s.u. is ___
A. \[4.78 \times {10^{ - 10}}\]
B. \[ + 1.6 \times {10^{ - 19}}\]
C. \[2.99 \times {10^9}\]
D. \[ - 1.6 \times {10^{ - 19}}\]

Answer 1

Hint: In Physics, quantum means the minimum possible value of an entity or a quantum is the minimum amount of any physical entity involved in an interaction. The fundamental notion that a physical property can be "quantized" is referred to as "the hypothesis of quantization".
e.s.u. means the electrostatic system of units is a system of units used to measure quantities of electric charge, electric current, and voltage within the centimeter–gram–second system of metric units.

Complete answer:
Let us first understand what is meant by the word quantum.
In physics, quantum means the minimum possible value of an entity. The plural of quantum is quanta. Then it said that the magnitude of that entity can only be an integer multiple of one quantum.
Consider a pack of balls. Let us say that here the magnitude is the total number of balls in the pack. The minimum number of balls in the pack is one (the pack has at least one ball for sure). The ball is one quantum. Then the total number of balls in the pack will only be an integer multiple of this quantum number. It cannot be any other value.
Similarly, the quantity charge is also quantized. The value of one quantum is equal to the magnitude of the charge on an electron. We know that the magnitude of charge on an electron in coulomb is \[ + 1.6 \times {10^{ - 19}}\] and in e s u is \[4.78 \times {10^{ - 10}}\] .
Hence, the quantum of electric charge in e s u is \[4.78 \times {10^{ - 10}}\] .
Therefore, the correct option is (A).

Note:
Let us discuss why an electron is chosen as the one quantum. This is simply because electrons and protons are the fundamental charged particles and also the charges are made up of some whole numbers of electrons. That is a charge on a body is an integer multiple of e.