Correct Answer - Option 4 : the viscosity of the liquid is increased
Concepts:
The sensitiveness of a bubble tube depends upon the following:
- The radius of curvature of the internal surface i.e., larger the radius greater is the sensitiveness.
- The diameter of the bubble i.e., the larger the diameter, the greater the sensitiveness.
- The length of the bubble i.e., the larger the length greater is the sensitiveness.
- The viscosity and surface tension of the liquid i.e., lesser the viscosity more is its sensitiveness.
- Smoothness of the finish of the tube's internal surface i.e., greater the smoothness more is the sensitivity.
- Length of one division i.e., greater the length of one division more is the sensitiveness.
Note:
The sensitivity of the Bubble tube is given by the following expression
\(\alpha = \frac{S}{nD} = \frac{l}{R}\)
Where
α is the sensitivity of the bubble tube i.e. angle of rotation in radian due to one division of movement of the bubble.
n is the divisions moved by bubble.
l is the length of one division.
S is staff intercept and it is given as
S = S2 – S1
S1 is the staff reading when the bubble is exactly at the center or actual staff reading.
S2 is the staff reading when bubble moves some n divisions.
R is the radius of curvature of the Bubble Tube.