Physical quantity
Symbol
Dimensions
Unit
Remarks
Vector area element
D S
[L2]
m2
DS = DS ˆn
Electric field
E
[MLT–3A–1]
V m–1
Electric flux
f
[ML3 T–3A–1]
V m
Df  =  E DS
Dipole moment
p
[LTA]
C m
Vector directed
from negative to
positive charge
Charge density:
linear
l
[L–1 TA]
C m–1
 Charge/length
surface
s
[L–2 TA]
C m–2
Charge/area
volume
r
[L–3 TA]
C m–3
Charge/volume
POINTS TO PONDER
1 You might wonder why the protons, all carrying positive charges,
are compactly residing inside the nucleus Why do they not fly away