Electric Charges and Fields — Physics STD 12 Science — Question
Bihar BoardEnglish MediumSTD 12 SciencePhysicsElectric Charges and Fields2 Marks
Question
Explain : Why we can consider quantisation of charge for microscopic level but not for macroscopic level ?
✓
Answer
►The size of e is, however, very small because at the macroscopic level, we deal with charges of a few $\mu C$. ►At this scale the fact that charge of a body can increase or decrease in units of $e$ is not visible. ►In this respect, the particle nature of the charge is lost and it appears to be continuous. This situation can be compared with the geometrical concepts of points and lines. A dotted line viewed from a distance appears continuous to us but is not continuous in reality. As many points very close to each other normally give an impression of a continuous line, many small charges taken together appear as a continuous charge distribution. ►At the macroscopic level, one deals with charges that are enormous compared to the magnitude of charge $e$. Since $e=1.6 \times 10^{-19} C$, a charge of magnitude, say $1 \mu C$, contains something like $10^{13}$ times the electronic charge. ►At this scale, the fact that charge can increase or decrease only in units of $e$ is not very different from saying that charge can take continuous values. ►Thus, at the macroscopic level, the quantisation of charge has no practical consequence and can be ignored. However, at the microscopic level, where the charges involved are of the order of a few tens or hundreds of e, i.e., they can be counted, they appear in discrete lumps and quantisation of charge cannot be ignored.
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