Units vs. Quantities in electromagnetism

By Tutor GuyNo Comments

 

Keeping the abbreviations straight in electromagnetism is particularly hard because sometimes the abbreviation we use for a QUANTITY is the same letter we use to define a UNIT of a different quantity. For example, a capital C is used for capacitance in the equation C = Q/V. But in the statement Q = 0.050 C, the C stands for ‘coulomb’, the unit of charge. It is up to you to understand from the context whether the symbol refers to a quantity or a unit.

Also, the symbol for a QUANTITY often comes from a German abbreviation, so it’s not the letter you expect. For example, the symbol for inductance is L, not I, and the symbol for current is I, not C. Again, it’s up to you to learn these well enough that you can figure them out on your own. Here’s a table that shows the various symbols:

Quantity

Symbol   for quantity

Unit

Symbol   for unit

force

F

newton

N

charge

Q

coulomb

C

electric field

E

N/C or V/m

current

I

ampere

A

potential difference

V

volt

V

resistance

R

ohm

Ω

power

P

watt

W

capacitance

C

farad

F

magnetic flux

Φ

weber

Wb

inductance

L

henry

H

magnetic field

B

tesla

T

Physics
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