ANS:C - 17.2

=		2994	x	1		[ Here, Substitute 172 in the place of 2994/14.5 ]
		14.5		10

ANS:C - Agenda

No answer description is available. 

ANS:D - friend

No answer description is available. Let's discuss.

ANS:A - repetition

Measurement of Horizontal Angles.

a) Repetition Method: This method is used for very accurate work. In this method, the same angle is added several times mechanically and the correct value of the angle is obtained by dividing the accumulated reading by the no. of repetitions. The No. of repetitions made usually in this method is six, three with the face left and three with the face right. In this way, angles can be measured to a finer degree of accuracy than that obtainable with the least count of the vernier.

b) Reiteration Method. This method is another precise and comparatively less tedious method of measuring horizontal angles. It is generally preferred when several angles are to be measured at a particular station. This method consists of measuring several angles successively and finally closing the horizon at the starting point.

ANS:C - the denominator of Z(s) is one degree higher than numerator

No answer description is available.

ANS:A - N_sh = 2

The JD (Jakob and Dhanasekharan) factor is used to account for the effect of fluid flow on mass transfer in mass transfer processes. However, the JD factor is not directly related to Reynolds number in the same way as other dimensionless numbers like the Sherwood number (Nsh) for mass transfer, Nusselt number (Nst) for heat transfer, or Schmidt number (Nsc) for mass transfer in forced convection. When mass transfer occurs by molecular diffusion from a single drop to surrounding still air, it is typically characterized by the Sherwood number (Nsh), not the JD factor. The Sherwood number relates the mass transfer rate to the molecular diffusion rate and is a function of the geometry and flow conditions. Given that the diffusion is occurring from a single drop to surrounding still air, the Sherwood number (Nsh) would depend on factors such as the drop diameter, diffusivity of the species, and temperature gradient. The specific value of Nsh would need to be determined based on the specific conditions of the system. Therefore, the correct answer is: none of these.

ANS:B - compressed air

The air vessel of a reciprocating pump is initially filled with atmospheric air. Here's why: An air vessel is used in reciprocating pumps to smooth out the pulsating flow and reduce pressure fluctuations. When the pump is initially installed and the air vessel is fitted, it is open to the atmosphere, meaning it is filled with atmospheric air. As the pump starts operating, the air in the vessel gets compressed and acts as a cushion to absorb the energy fluctuations caused by the reciprocating action of the pump, leading to a more steady flow of the fluid. Therefore, the initial filling of an air vessel in a reciprocating pump is with atmospheric air.

ANS:B - Foreign Secretary

Vinay Mohan Kwatra got a 16-month extension as foreign secretary from Jan 01.

ANS:B - wetting characteristics

wetting characteristics

Explanation:

1. Hydrophobic vs. Hydrophilic

• Hydrophobic Materials: These do not readily interact with water and resist wetting. In froth flotation, hydrophobic ore particles attach to air bubbles and float to the surface.
• Hydrophilic Materials: These easily interact with water and are wetted by it. Hydrophilic particles tend to sink in the flotation process.

2. Surface Tension and Contact Angle

• Surface Tension: The cohesive force between liquid molecules affects how a liquid interacts with solid surfaces. Lower surface tension can improve the wetting of hydrophobic materials.
• Contact Angle: This is the angle formed at the liquid-solid interface. A smaller contact angle indicates better wetting, while a larger contact angle indicates hydrophobicity. For effective flotation, hydrophobic particles typically have higher contact angles.

3. Role in Froth Flotation

• Selective Separation: By modifying the surface properties of ore particles (often using surfactants), flotation can selectively separate valuable minerals from gangue based on their wetting characteristics.
• Bubble Attachment: Hydrophobic particles adhere to air bubbles and rise to the surface, forming a froth, while hydrophilic particles remain in the slurry.

Summary

ANS:B - 2022-23

Pre-matric scholarship will be given for minority students to only those in classes 9 & 10 from 2022-23; earlier from classes 1 to 10.