Electromagnetic Unit Names
(For non-electromagnetic units, see main cgs article.)
| Quantity | Symbol | SI unit | Gaussian unit |
|---|---|---|---|
| electric charge | q | 1 C | ↔ (10−1 c) Fr |
| electric current | I | 1 A | ↔ (10−1 c) Fr/s |
| electric potential voltage |
φ V |
1 V | ↔ (108 c−1) statV |
| electric field | E | 1 V/m | ↔ (106 c−1) statV/cm |
| magnetic induction | B | 1 T | ↔ (104) G |
| magnetic field strength | H | 1 A/m | ↔ (4π 10−3) Oe |
| magnetic dipole moment | μ | 1 A·m² | ↔ (103) erg/G |
| magnetic flux | Φm | 1 Wb | ↔ (108) G·cm² |
| resistance | R | 1 Ω | ↔ (109 c−2) s/cm |
| resistivity | ρ | 1 Ω·m | ↔ (1011 c−2) s |
| capacitance | C | 1 F | ↔ (10−9 c2) cm |
| inductance | L | 1 H | ↔ (109 c−2) s2/cm |
In this table, the letter c represents the number 29,979,245,800 ≈ 3·1010, the numerical value of the speed of light expressed in cm/s. The symbol "↔" was used instead of "=" as a reminder that the SI and Gaussian units are corresponding but not equal because they have incompatible dimensions. For example, according to the top row of the table, something with a charge of 1 C also has a charge of (10−1 c) Fr, but it is usually incorrect to replace "1 C" with "(10−1 c) Fr" within an equation or formula.
It is surprising to think of measuring capacitance in centimetres. One useful example is that a centimetre of capacitance is the capacitance between a sphere of radius 1 cm in vacuum and infinity.
Another surprising unit is measuring resistivity in units of seconds. A physical example is: Take a parallel-plate capacitor, which has a "leaky" dielectric with permittivity 1 but a finite resistivity. After charging it up, the capacitor will discharge itself over time, due to current leaking through the dielectric. If the resistivity of the dielectric is "X" seconds, the half-life of the discharge is ~0.05X seconds. This result is independent of the size, shape, and charge of the capacitor, and therefore this example illuminates the fundamental connection between resistivity and time-units.
Read more about this topic: Gaussian Units
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