Barometer Important Questions

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Very Short Answers Questions [1 Mark Questions]

Ques. In the space above the mercury column in a barometer tube, the gauge pressure of the vapor is

1. Negative
2. Positive, but more than 1 atm
3. Positive, but less than 1 atm
4. Zero

Ans. The correct answer is a. Negative

Explanation: The gauge pressure of the vapor is negative in the space above the mercury column in a barometer tube.

Ques. If a hole is made in the Torricelli's vacuum portion of a barometer, then the mercury

1. the level will oscillate between the reservoir level and the original level of the mercury in the stem
2. will spill through the hole made
3. level will fall in the stem and the mercury will collect in the reservoir
4. level in the stem will remain at the same level indicating atmospheric pressure

Ans. The correct answer is c. level will fall in the stem and the mercury will collect in the reservoir

Explanation: If the vacuum portion has a hole, there will be no pressure difference between the top and bottom of the stem. The mercury in the stem will read zero, indicating that it will fall and collect in the reservoir.

Ques. Mercury is used in barometers because of its

1. High-density
2. High melting point
3. High boiling point
4. Low melting point

Ans. The correct answer is a. High-density

Explanation: Mercury is used in barometers because it is a high-density fluid with a low column height at high pressures.

Ques. Ques. The instrument for measuring blood pressure is called:

1. Manometer
2. Potentiometer
3. Sphygmomanometer
4. Barometer

Ans. The correct answer is c. Sphygmomanometer

Explanation: A sphygmomanometer is a blood pressure measuring device that is also known as a blood pressure meter, blood pressure gauge, or blood pressure monitor.

Ques. In a barometer, mercury is preferred over water because

1. Mercury is shining and therefore its level can be read easily
2. Mercury is available in pure form
3. Mercury is a good conductor of heat
4. Mercury has high density and low vapor pressure

Ans. The correct answer is d. Mercury has high density and low vapor pressure

Explanation: Mercury, instead of water, is used in barometers because its high density allows for a sufficient height of the column to detect atmospheric pressure.

Ques. 1 bar is equal to

1. 10⁶ Pascal
2. 10⁵ Pascal
3. 10³ Pascal
4. 10² Pascal

Ans. The correct answer is b. 10⁵ Pascal

Explanation: Bar and Pascal are the units of pressure. One bar is equivalent to 10⁵ Pascal.

Ques. Viscosity is the measure of the

1. Hindrance to the flow of air
2. Hindrance to the flow of an object
3. Resistance to the flow of fluid
4. None of the above

Ans. The correct answer is c. Resistance to the flow of fluid

Explanation: Viscosity occurs at various velocities due to the relative motion of two fluid surfaces. This phenomenon occurs as a result of shear stress developing on the surface of the fluid.

Ques. In a stationary fluid, how does the local pressure of the fluid vary?

1. In the horizontal direction only
2. With depth only
3. Neither with depth nor along horizontal direction
4. Both with depth and along horizontal direction

Ans. The correct answer is b. With depth only

Explanation: The local pressure of a fluid is the same in all directions, according to Pascal's law. As a result, the pressure will remain constant in the x and y directions. The extra weight of the water column above that location causes the local pressure to rise as depth increases.

Ques. The pressure measurement cannot be carried out accurately by a manometer for dynamic fluid motion in a pipe.

1. True
2. False

Ans. The correct answer is a. True

Explanation: A manometer cannot be used because changes in pressure are frequent and greater in magnitude for fluid flowing at different velocities.

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Short Answers Questions [2 Marks Questions]

Ques. What is a barometer?

Ans. A barometer is a scientific device that measures the air pressure in a given location. Changes in air pressure can predict short-term changes in the weather. Meteorologists use surface weather analysis and barometer readings to identify surface troughs, pressure systems, and frontal boundaries.

Ques. What is a mercury barometer?

Ans. A mercury barometer is a device that uses a column of mercury to detect atmospheric pressure. The mercury barometer is the earliest form of barometer, which was designed in 1643-44 by Evangelista Torricelli, an Italian physicist and mathematician. In its simplest form, it consists of a narrow glass tube closed at one end and open at the other, submerged in a pool of mercury. As air pressure changes the height of the mercury in the tube changes.

Ques. What is an aneroid barometer?

Ans. An aneroid barometer is a non-liquid barometer that is widely used in aviation altimeters and portable devices due to its small size and applicability. It consists of an evacuated capsule with a flexible wall that deflects with changes in air pressure.

Ques. What is pressure?

Ans. Pressure is defined as the force applied perpendicular to an object's surface per unit area across which that force is distributed. Gauge pressure is the pressure with the surrounding atmosphere. Pressure is expressed using a variety of units.

Ques. Why is mercury used in barometers?

Ans. Mercury is used in barometers because it is a high-density fluid with a low column height at high pressures. To generate the same pressure difference, a water barometer, for example, would need to be 13.6 times taller than a mercury barometer. This is because mercury is 13.6 times denser than water.

Ques. What is meant by 1 bar of pressure?

Ans. The bar is a metric pressure unit that is defined as 100,000 Pa (100 kPa). A pressure of 1 bar is somewhat lower than the current average atmospheric pressure at sea level on Earth (about 1.013 bar). According to the barometric formula, 1 bar is about the atmospheric pressure on Earth at a height of 111 meters at 15 degrees Celsius.

Ques. Define atmospheric pressure.

Ans. The pressure within the atmosphere of the Earth is known as atmospheric pressure, sometimes known as air pressure or barometric pressure. A standard atmosphere is a pressure unit defined as 101,325 Pa, which is comparable to 1,013.25 millibars, 760 millimeters of mercury, 29.9212 inches of mercury, or 14.696 pounds per square inch.

Ques. What are the different types of pressure?

Ans. The different types of pressure are

• Absolute pressure
• Gauge pressure
• Differential pressure
• Sealed pressure or vacuum pressure

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Long Answers Questions [3 Marks Questions]

Ques. How will you show that there is a vacuum above the surface of the mercury in a barometer? 

Ans. If a drop of water or alcohol is put into the space above the mercury column, the barometric height falls as liquid (water or alcohol) vaporizes in the vacuum and exerts pressure on the surface of mercury, pushing it to fall. The vacuum is known as a Torricellian vacuum.

• The barometer consists of a glass tube that is closed at one end and has an open reservoir of mercury at the other. 
• The weight of mercury forms a Torriceilian vacuum at the top of the tube. 
• The mercury in the tube adjusts until the weight of the mercury column equals the atmospheric force on the reservoir. 
• There is no space for air to enter. 
• As there is no breaking in the glass tube, there will be simply a vacuum when the mercury falls.

Ques. What are the different types of barometers?

Ans. The following are the different types of barometers

• Mercury Barometer: A mercury barometer is made up of a glass tube filled with mercury that is inverted into a dish of mercury. The weight of the mercury creates a vacuum at the top of the tube, and when air pressure changes, the mercury level rises or falls, showing pressure differences.
• Aneroid Barometer: An aneroid barometer is made up of a sealed, flexible metal chamber that expands and contracts in response to variations in atmospheric pressure. The pressure is measured by mechanically translating this expansion or contraction into a dial reading.
• Digital Barometer: A digital barometer measures air pressure using electronic sensors and displays the measurement on a digital screen. Digital barometers are convenient and accurate, and they frequently include functions such as weather trend indicators and altitude information.

Ques. How does a Barometer work?

Ans. A barometer works by balancing the weight of mercury in a glass tube with the weight of the atmosphere. 

• High atmospheric pressure pushes a plastic wrap inside the tube, tilting the end of a straw taped to the plastic and the bottom of the tube. 
• If the weight of mercury in the tube is less than the atmospheric pressure, the mercury rises. 
• If the weight of mercury is greater than the atmospheric pressure, the mercury falls. 
• The atmospheric pressure can be measured by reading the marked line on the glass tube where the mercury stops.

Ques. How is the barometer used for forecasting weather?

Ans. The following are the ways for a barometer to be used in weather forecasting

• If the barometric level decreases without any increase in the moisture content of the air, it indicates the approach of a dusty storm.
• If the barometric pressure drops and the moisture content of the air rises, it indicates that rain is approaching.
• If the barometric pressure gradually decreases and the moisture content of the air rises, it indicates the weather is going to gradually change to rainy.
• If the barometric pressure drops suddenly and the moisture content of the air rises, it indicates a rainstorm, storm, or cyclone is approaching.
• If the barometric pressure gradually increases and the moisture content of the air decreases, it indicates the weather is gradually shifting to dry weather.
• If the barometric pressure suddenly rises, it indicates that the weather is dry but might change to anti-cyclonic.

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Very Long Answers Questions [5 Marks Questions]

Ques. What is the difference between a manometer and a barometer?

Ans. The following are the differences between a manometer and a barometer

Ques. What are the applications of barometers?

Ans. The following are the applications of barometers

• Barometers for weather forecasting: Barometers are essential for weather forecasting. They help meteorologists track changes in atmospheric pressure, which can predict the arrival of weather systems. A sudden pressure drop may indicate an approaching storm, while a steady rise suggests stable weather conditions.
• Barometers for altitude measurement: Barometers are useful for estimating altitude, particularly in places where typical altimeters are either unavailable or unreliable. Hikers, climbers, and pilots can correctly measure their height using barometers, which analyze pressure variations with altitude.
• Barometers in aviation: Barometers are essential in aviation for estimating altitude, adjusting flight levels, and assuring aircraft safety. To maintain the appropriate height and navigate across varied air pressure zones, pilots rely on precise barometer readings.
• Barometers in marine navigation: Barometers are important in maritime navigation because they help sailors predict storms, recognize changing weather patterns, and maintain safe sailing conditions. Understanding barometric patterns can help sailors in making educated judgments when at sea.
• Barometers in home and garden: Barometers can also be used in homes and gardens for a variety of practical purposes. They can help people monitor and adjust indoor humidity levels, plan outdoor activities based on upcoming weather changes, and even make gardening decisions based on changes in atmospheric pressure.
• Barometers in scientific research: Barometers are used by scientists and researchers in a variety of scientific areas. For experiments, observations, and environmental monitoring, they rely on precise pressure readings. Barometers help in the study of atmospheric phenomena, climate patterns, and other scientific investigations.

Ques. What are the advantages and disadvantages of a barometer?

Ans. The following are the advantages and disadvantages of a barometer

Advantages:

• Because mercury has a high density, the height of the column can be a suitable size for measuring atmospheric pressure.
• Because mercury is opaque, accurate measurements can be obtained.
• Mercury moves quickly over glass, but water adheres to the surface.
• A barometer has a high density as well. It also has great sensitivity and can detect even the smallest changes in pressure.
• It also has a very simple design, making it easy to maintain.

Disadvantages:

• Barometers can be fragile and difficult to transport.
• Barometers can be inaccurate if they are not calibrated properly.
• Barometers can be affected by changes in temperature and altitude.
• Barometers can be difficult to read, especially in low light conditions.

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