NEET-XII-Physics
01: Electric Charges And Fields
- #3Check that the ratio ke2/G memp is dimensionless. Look up a Table of Physical Constants and determine the value of this ratio. What does the ratio signify?
Ans : The given ratio is
.
Where,
G = Gravitational constant
Its unit is N m2 kg-2.
me and mp = Masses of electron and proton.
Their unit is kg.
e = Electric charge.
Its unit is C.
`` \epsilon``0 = Permittivity of free space
Its unit is N m2 C-2.
Hence, the given ratio is dimensionless.
e = 1.6 × 10-19 C
G = 6.67 × 10-11 N m2 kg-2
me= 9.1 × 10-31 kg
mp = 1.66 × 10-27 kg
Hence, the numerical value of the given ratio is
This is the ratio of electric force to the gravitational force between a proton and an electron, keeping distance between them constant.