Register to reply 
Problem with unitsby Henk
Tags: units 
Share this thread: 
#1
Oct1405, 06:41 AM

P: 22

I'm having great difficulties with CGSunits. In an experiment involving NMR I have to calculate the protonproton distance in CaSO4.2H2O.
I have done the measurements and they are, I think, pretty good however I have some problems with the calculations because of the units. The formula I have to use is the following: a = (3/2)(u*u0)/r^3 where u = 2.79*5.05*10^27 J/T = 2.79*5.05*10^24 erg/Gauss and u0 is the Permeability of vacuum. a is something I measured and has a value of 4.5 Gauss. I know that r should be about 1.5 Angstrom (spelling?). My instructor told me to use CGSunits (thus putting u0=1) but does that mean that the rest of the formula stays the same? Or are there other changes like an additional 4pi or something. If I just put u0=1 I get r = 1.67*10^8 (but I don't know the units, I believe the CGSunit for distance is cm in which case r=1.67*10^10 m = 1.67 A which is pretty close to 1.5 A). 


#2
Oct1505, 04:02 AM

Emeritus
Sci Advisor
PF Gold
P: 6,236

So I then do everything in SI units, and fill in the 4 pi in the other units in order to obtain the same result 


Register to reply 
Related Discussions  
I have a problem with units...  General Physics  1  
FAQ:What's the differences between Radiometric Units and Photometric Units?  Introductory Physics Homework  2  
Units problem..  Introductory Physics Homework  2  
Units problem  Introductory Physics Homework  15  
Maxwell related equations converted from MKSA units to Gaussian units  Classical Physics  2 