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# Charge in the CGS system

last edited by 1 year, 2 months ago

4.2.4.P20

In this class, we mostly use the SI units system, which measures charge in Coulombs. Some physicists use the CGS system, which has only centimeters, grams, and seconds (hence the name). In this system, Coulomb's law has the equation

Felectq→Q = qQ/r2

There is no constant like  in this system. Instead, charge itself has dimensions of mass, length, and time in some combination. That is, in this system

[Q] = MaLbTc

1a - What is a?

1b - What is b?

1c - What is c?

2 - Charge in this system is measured in terms of statcoulombs, statC. Two charges each having a charge of 1 statC at a distance apart of 1 cm, will repel each other with a force of 1 dyne (= 1 gram-cm/sec2).

Find the charge on an electron in statC. Show your work in doing the conversion. Don't just look up the answer! (Though you might do that to check your result.)

Note: This is a multi-step unit conversion. Take your time and be careful!

3 - Can you think of an advantage to doing dimensional analysis in CGS rather than SI? A disadvantage? Or does it not matter?

Mark Eichenlaub 10/2/17