CGPET 2015 Solved Paper

Height or depth of liquid column in the capillary tube
y=

2S‌cos‌θ

rδg

where, S = surface tension of the liquid
θ = angle of contact
r = radius of the tube
ρ = density of the liquid
For water,
h=

2Sw‌cos‌θ

rρwg

......(i)
For mercury,
d=

2Sm‌cos‌θ

rρmg

..... (ii)
From Eqs. (i) and (ii),

h

d

=

Sw

Sm

×

ρm

ρw

×

cos‌0°

cos‌135°

⇒

10

−3.42

=

Sw

Sm

×13.6×

1

( −1 √2 )

⇒

10

−3.42

=

Sw

Sm

×13.6×√2
or,

Sw

Sm

=

10

3.42

×

1

13.6

×

1

√2

=1:6.57