Elementary charge

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The elementary charge (symbol: e) is a physical constant equal to the absolute electric charge of a proton or an electron. The 2006 CODATA recommended value is e = 1.602 176 487(40) × 10−19 C.[1]

Measurement

In the most recent CODATA adjustments,[1] the elementary charge is not an independently refined quantity. Instead, a consistent value is derived from the relation e2 = /μ0c0, where h is the Planck constant, α is the fine structure constant, μ0 is the magnetic constant and c0 is the speed of light. The uncertainty in the value of e is currently determined entirely by the uncertainty in the Planck constant.[note 1]

Notes and references

Notes

  1. In the current SI system, μ0 and c0 are fixed by the definitions of the ampere and the metre respectively. The relative uncertainty in α is almost 100-times lower than the relative uncertainty in h.

References

External links

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