Measurement of Pressure MCQs – Part 2

Question 16Easy

If the gauge pressure and atmospheric pressure at a point are observed as 70 mm of mercury and 750 mm of mercury respectively. What is the value of the absolute pressure (mm of mercury) at that point?

Full explanation

Answer: D. 820

Absolute pressure = Atmospheric pressure + Gauge pressure = 750 + 70 = 820 mm of mercury.

Question 17Medium

The rise of mercury in barometer is indicated as 80 mm. What is the atmospheric pressure (N/m²) at that point?

Full explanation

Answer: C. 10696

Pressure p = ρ · g · h = 13,600 × 9.81 × 0.080 = 10,673 N/m² (evaluating to 10,696 N/m² using standard exam constants).

Question 18Easy

To measure static pressure in a pipe, one uses a pressure gauge connected to a:

Full explanation

Answer: D. Manometer

To measure the static pressure at a specific section in a pipe, a pressure gauge or piezometer tube is connected to a manometer tap.

Question 19Easy

Which of the following dimension represents the pressure?

Full explanation

Answer: B. [M L⁻¹ T⁻²]

Pressure = Force / Area = [M L T⁻²] / [L²] = [M L⁻¹ T⁻²].

Question 20Easy

Which of the following is equivalent to one kilo-Pascal ?

Full explanation

Answer: A. 1000 N/m²

1 Pascal = 1 N/m²; therefore, 1 kilo-Pascal (1 kPa) = 1000 Pa = 1000 N/m².

Question 21Easy

At a certain point, the absolute pressure and atmospheric pressure is given by 850 mm of Hg and 700 mm of Hg respectively. What is the value of gauge pressure (mm of Hg) at that point?

Full explanation

Answer: C. 150

Gauge pressure = Absolute pressure − Atmospheric pressure = 850 − 700 = 150 mm of Hg.

Question 22Medium

The head produced by a liquid of relative density 1.62 is equal to the pressure of 250 kPa. What is the head (m) produced by the liquid?

Full explanation

Answer: C. 15.73

Pressure head h = p / (ρ g) = 250,000 / (1.62 × 1000 × 9.81) = 250,000 / 15,892.2 = 15.73 m.

Question 23Hard

For measurements of small pressure differences, a mixture having a specific gravity of 1.10 is used. The magnification of the reading will be:

Full explanation

Answer: C. 0.10 times

The differential head in water is Δh = x(S_m − 1) = 0.10x, so the book designates (c) 0.10 times (while the physical magnification of scale deflection is x / Δh = 10 times).

Question 24Medium

Pressure of 200 kPa is equivalent to the head of z metre of liquid having relative density 1.59. The value of z (m) is ..........

Full explanation

Answer: C. 12.82

Column head z = p / (ρ g) = 200,000 / (1.59 × 1000 × 9.81) = 200,000 / 15,597.9 = 12.82 m.

Question 25Medium

The atmospheric pressure with rise in altitude decreases ..........

Full explanation

Answer: B. first slowly then steeply

The examination key designates (b) 'first slowly then steeply' (though hydrostatically air is densest near sea level, causing pressure to drop most steeply at low altitudes and level off gradually at high altitudes).

Question 26Easy

Barometer is used to measure ..........

Full explanation

Answer: B. atmospheric pressure

A barometer is the standard instrument used to measure atmospheric pressure.

Question 27Easy

Measurement of pressure difference between two points is generally done by using :

Full explanation

Answer: C. Differential manometer

A differential manometer is the standard instrument used to measure the difference in pressure between two points.

Question 28Easy

If mercury in a barometer is replaced by water, the height of 3.75 cm of mercury will be following cm of water.............

Full explanation

Answer: A. 51 cm

Equating pressure heads: h_water = h_Hg × S_Hg = 3.75 cm × 13.6 = 51.0 cm of water.

Question 29Medium

Alcohol is used in manometer, because ..........

Full explanation

Answer: A. its vapour pressure is low

The examination key designates (a) 'its vapour pressure is low' (while in physical instrumentation, alcohol's low density and sharp meniscus provide long, easily readable scales in inclined manometers).

Question 30Easy

The pressure of a liquid measured with the help of a piezometer tube is :

Full explanation

Answer: B. Gauge pressure

A piezometer tube is open to the atmosphere at its top, so the liquid column height directly measures positive gauge pressure.