Resistance SI units

Conductance (G,g) is the reciprocal of resistance and has units of reciprocal ohms or mhos (fi" ) or more properly in SI units, seimens. 

Table 22.9 Water-carrying capacity of pipes (SI units) (approximate frictional resistance in mbar per m of travel)...

The SI unit of current I is the ampere (A). An ampere was first defined as the current flowing when a charge of 1 C (coulomb) passed per second through a perfect (i.e. resistance-free) conductor. The SI definition is more rigorous the ampbre is that constant current which, if maintained in two parallel conductors (each of negligible resistance) and placed in vacuo 1 m apart, produces a force between of exactly 2 x 10-7 N per metre of length . We will not employ this latter definition. 

I = EIR where I is the current, E is the electromotive force, and R is the resistance. The SI units for each of these is amperes, volts, and ohms, respectively. Ohm s law is also expressed as / = AE/7 where AE is the difference in electric potential. The resistance is dependent upon the dimensions of the conductor. 

A reference frame that, while resisting unambiguous definition, serves to measure the progress/motion of chemical/physical processes. The SI unit for time is the second (symbohzed as s). See Time Chronomals... 

The SI unit for electric potential and for electromotive force (symbolized by V) equivalent to one joule per coulomb. It is the difference in electric potential needed for a one ampere current to flow through a resistance of one ohm. 

The fact that the velocity of a fluid changes from layer to layer is evidence of a kind of friction between these layers. The layers are mathematical constructs, but the velocity gradient is real and a characteristic of the fluid. The property of a fluid that describes the internal friction or resistance to flow is the viscosity of the material. Chapter 4 is devoted to a discussion of the measurement and interpretation of viscosity. For now, it is enough for us to recall that this property is quantified by the coefficient of viscosity 77 of a material. The coefficient of viscosity has dimensions of mass length-1 time-1, kg m-ls-1 in SI units. In actual practice, the cgs unit of viscosity, the poise (P), is widely used. Note that pure water at 20°C has a viscosity of about 0.01 P = 10-3kgm-ls-1... 

OHM (ft). A unit of resistance (and of impedance). The resistance of a conductor such that a constant cunent of 1 ampere m it produces a voltage diffei tnces of 1 volt between its ends. (The SI unit of resistance.)... 

Note that an italicized V is the potential difference whereas a non-italicized V is the SI unit known as the volt. Additionally, a volt divided by an ampere is called an ohm, Q, the SI unit of resistance ... 

Resistance — Electrical resistance is the property of a material to resist or oppose the flow of an electrical -> current. The SI unit of resistance is the ohm (given the Greek symbol Q). The reciprocal of resistance is -> conductance, measured in siemens (S). The resistance of a material determines the magnitude of -> current that flows for a given -> voltage applied across the material, as given by -> Ohms law, AE = I-R, where AE is the potential difference across the material measured in -> volts,... 

Because the meter is inconveniently large for measuring the dimensions of most samples in material studies, you will frequently see p expressed in units of cm and tr in units of (fl cm) . Be alert to the actual units used. In base International System of Units (SI), resistivity has units expressed as kg m ... 

Electrolytic conductivity is the ability of an electrolytic solution to conduct electricity between two electrodes across which an electric field is applied. Ohm s law, V = I R, is obeyed and the magnitude of the current depends, in part, on the magnitude of the applied potential. The conductance, G, of a solution is expressed in terms of the solution electrolytic resistance. It is measured in reciprocal ohms (mhos) or in the SI unit siemens (S). 

---