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Grade 11Thermal Physics

I HAVE FOLLOWING DOUBTS..

1)TWO SPHERICAL FLASKS HAVING A VOLUME V=1L EACH CONTAINING AIR ARE CONNECTED BY A TUBE OF DIAMETER D=6MM AND LENGHT L=1M..A SMALL DROPLET OF MERCURY CONTAINED IN THE TUBE IS AT THE MIDDLE AT 273K ..BY WHT DISTANCE DO MERCURY DROPLETS MOVE IF FLASK 1 IS HEATED BY 2'C AND FLASK 2 IS COOLED BY 2'C..

2)A NON CONDUCTING CYLINDRICAL VESSEL OF LENGHT 3L IS PLACED HORIZONTAL;LY AND IS DIVIDED INTO 3 PARTS BY 2 EASILY MOVING PISTONS HAVIN LOW THERMAL CONDUCTIVITY ..THESE PARTS CONTAIN H2 HE AND CO2 GA AT INITIAL TEMP 372'C , -15'C , 157'C RESPECTIVELY..IF INITIAL LENGHT AND PRESSURE OF EACH AARE L AND P RESPECTIVELY , CALCULATE FINAL PRESSURE AND LENGHT OF EACH PART..(GIVEN Y FOR CO2 =1.4)

3)A BAROMETER IS FAULTY,,WHEN TRUE BAROMETER REAS 73 AND 75 CM OF HG, THE FAULTY READS 69 AND 70CM..

WHAT IS THE TOTAL LENGHT OF BAROMETER TUBE?

WHAT IS THE FAULTY READING WHEN TRUE READING IS 74CM?

Profile image of akhil  samir killawala
16 Years agoGrade 11
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1 Answer

Profile image of Askiitians Tutor Team
ApprovedApproved Tutor Answer1 Year ago

Let's tackle your questions one by one, starting with the first scenario involving the two spherical flasks and the movement of the mercury droplet. This problem involves concepts from thermodynamics and gas laws, particularly the ideal gas law and the behavior of gases under temperature changes.

Movement of Mercury Droplet in Connected Flasks

In this setup, we have two flasks containing air, connected by a tube with a mercury droplet in the middle. When Flask 1 is heated by 2°C and Flask 2 is cooled by 2°C, the change in temperature will affect the pressure of the gases in each flask, causing the mercury to move.

Understanding the Pressure Change

According to the ideal gas law, the pressure of a gas is directly proportional to its temperature when the volume is constant. The formula can be expressed as:

  • P1/T1 = P2/T2

Where P is pressure and T is temperature in Kelvin. The initial temperature of both flasks is 273 K. After the temperature changes, we have:

  • Flask 1: T1 = 273 K + 2 K = 275 K
  • Flask 2: T2 = 273 K - 2 K = 271 K

Calculating Pressure Changes

Assuming the initial pressure in both flasks is P0, we can find the new pressures:

  • For Flask 1: P1 = P0 * (275 K / 273 K)
  • For Flask 2: P2 = P0 * (271 K / 273 K)

Now, the difference in pressure (ΔP) between the two flasks will cause the mercury to move. The pressure difference can be calculated as:

  • ΔP = P1 - P2 = P0 * (275/273 - 271/273)

Calculating this gives:

  • ΔP = P0 * (4/273)

Movement of Mercury

The movement of the mercury droplet can be calculated using the hydrostatic pressure equation:

  • ΔP = ρgh

Where ρ is the density of mercury (approximately 13,600 kg/m³), g is the acceleration due to gravity (9.81 m/s²), and h is the height the mercury moves. Rearranging gives:

  • h = ΔP / (ρg)

Substituting ΔP into this equation will allow you to find the distance the mercury moves. You can plug in the values to get the final answer.

Pressure and Length in a Non-Conducting Cylindrical Vessel

Now, let’s move on to the second question about the non-conducting cylindrical vessel divided into three parts. Each part contains different gases at varying temperatures.

Initial Conditions

We have:

  • Part 1: H2 at 372°C
  • Part 2: He at -15°C
  • Part 3: CO2 at 157°C

Convert these temperatures to Kelvin:

  • H2: 372 + 273 = 645 K
  • He: -15 + 273 = 258 K
  • CO2: 157 + 273 = 430 K

Using the Ideal Gas Law

The pressure in each part can be calculated using the ideal gas law, which states:

  • P1V1/T1 = P2V2/T2

Assuming the volume of each part is L, the initial pressure is P, and the lengths of each part are L1, L2, and L3 respectively, we can express the final pressures after equilibrium is reached. Since the pistons can move, the pressures will equalize across the vessel.

Final Pressures and Lengths

After the system reaches thermal equilibrium, the final pressure in each part can be calculated based on the average temperature and the specific heat capacities of the gases. The final lengths will depend on the final pressures and the initial conditions. You can set up equations based on the conservation of energy and the ideal gas law to solve for the final states.

Faulty Barometer Reading

For the last question regarding the faulty barometer, we need to analyze the relationship between the true readings and the faulty readings.

Establishing the Relationship

When the true barometer reads 73 cm, the faulty barometer reads 69 cm. When the true barometer reads 75 cm, the faulty barometer reads 70 cm. We can establish a linear relationship between the true reading (T) and the faulty reading (F):

  • F = T - 4

Using this relationship, we can find the total length of the barometer tube. The faulty reading when the true reading is 74 cm can be calculated as:

  • F = 74 - 4 = 70 cm

Calculating Total Length

The total length of the barometer tube can be inferred from the maximum true reading, which is 75 cm. Therefore, the total length of the barometer tube is 75 cm.

In summary, each of these problems involves applying fundamental principles of physics, including gas laws and thermodynamics, to find the solutions. If you have any further questions or need clarification on any of these points, feel free to ask!