Charge is Quantised — Q = Ne
Dial in a charge and watch it divided by the elementary charge. When the answer comes out a whole number you are shown that many electrons; when it does not, you are shown the fraction of an electron that cannot exist.
How to use this simulation
- Drag the charge slider and watch N = Q/e update as you go
- Press 1.6×10⁻¹⁸ C for a clean whole number of electrons
- Press 1.6×10⁻²⁰ C to see a charge smaller than the quantum itself
- Press 1.8×10⁻¹⁸ C for a value that divides into a fraction and is therefore impossible
What to look for
- Only whole values of N correspond to a charge that can physically exist
- 1.6 × 10⁻²⁰ C would be a tenth of one electron — below the quantum, so it is ruled out
- 1.8 × 10⁻¹⁸ C divides into 11.25 electrons, and the leftover quarter is what makes it impossible
- The smallest allowed non-zero charge is e itself, at N = 1
- Large charges have such huge N that quantisation stops being visible
The physics behind it
Charge comes only in whole multiples of the elementary charge e = 1.6 × 10⁻¹⁹ C, so any observable charge satisfies Q = Ne with N a positive integer. Dividing a proposed charge by e is therefore a test as well as a calculation: 1.6 × 10⁻¹⁸ C gives N = 10 and is allowed, while 1.6 × 10⁻²⁰ C would need a tenth of an electron and cannot occur. The quantum is small enough that everyday currents involve N in the range of 10¹⁸ and up, which is why charge looks continuous outside the laboratory.