Explain the meaning of the statement electric charge of a body is quantised, (b) Why can one ignore quantisation of electric charge when dealing with macroscopic, i.e., large scale charges?

a) Quantisation of electric charge means that the total electric charge on any body is always an integral multiple of the elementary charge ($e$). This means charge cannot take any arbitrary value, but only discrete values. The formula for quantisation of charge is: $q = \pm ne$ where $n$ is an integer ($0, 1, 2, \dots$) and $e$ is the elementary charge, approximately $1.6 \times 10^{-19} \, \text{C}$.

b) Quantisation of electric charge can be ignored when dealing with macroscopic (large-scale) charges because the magnitude of macroscopic charges is much larger than the quantum of charge ($e = 1.6 \times 10^{-19} \, \text{C}$). For example, a charge of $\pm 10^{-6} \, \text{C}$ contains approximately $10^{13}$ elementary charges. In such cases, the discrete nature of charge becomes insignificant, and charge can be treated as if it were continuous.