10 Question-answer on surface tension | Learn Physics

10 Question-answer on surface tension

1.       Surface tension of a liquid is due to:

(a)    Gravitational force between molecules

(b)   electrical force between molecules

(c)    adhesive force between molecules

(d)   cohesive force between molecules

Ans: ( d)

2.       Surface tension may be defined as:

(a)    The work done per unit area in increasing the surface area of a liquid under isothermal conditions

(b)   The work done per unit area in increasing the surface area of a liquid under adiabatic conditions

(c)    The work done per unit area in increasing the surface area of a liquid under adiabatic conditions

(d)   Free surface energy per unit volume

Ans: (a)

3.       Kerosene oil rises up in a wick of a lantern because of:

(a)    Diffusion of the oil through the wick

(b)   Surface tension

(c)    Buoyant force of air

(d)   The gravitational pull of the wick

Ans: (b)

4.       At critical temperature, the surface tension of a liquid is:

(a)    Zero

(b)   Infinity

(c)    The same as that at any other temperature

(d)   Cannot be determined

Ans: ( a)

5.       An iron needle slowly placed on the surface of water floats on it because

(a)    When inside water, it will displace water more than its weight

(b)   The density of material of needle is less than that of water

(c)    Of surface tension

(d)   Of its shape

Ans: ( c)

6.       A given mass of a metal is moulded into solids of different shapes. Its surface area is the least when it is:

(a)    A sphere

(b)   A right circular cylinder

(c)    A paraboloid

(d)   A right circular cone

Ans: (a)

7.       When a pinch of salt or any other salt which is soluble in water is added to water, its surface tension

(a)    Increases

(b)   decreases

(c)    may increase or decrease depending upon salt

(d)   none of above

Ans: (a)

8.       When a small quantity of impurity which is partially soluble, is added to water the surface tension of water :

(a)    Increases

(b)   decreases

(c)    may increase or decrease

(d)   none of above

Ans: (b)

9.       Two vertical glass plates 1 mm apart are dipped into water. How high will be the water rise between the plates, if the surface tension of water is 70 dyne/cm² .

(a)    2.86 cm

(b)   1.43 cm

(c)    5.72 cm

(d)   1.63 cm

Ans: (b)

10.       A liquid disturbed by stirring comes to rest after some time due to:

(a)    Surface tension

(b)   Stability

(c)    Viscosity

(d)   Attraction forces between molecules

Ans: ( c)