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## Speed of sound

Why sound travels faster in humid air than normal air as humid air is denser than normal air? (Akash asked) Answer: The speed of sound in a medium is inversely proportional to the square root of its density. Humid air is less dense than dry air. Therefore the speed of sounf in humid air is greater than that in […]

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## Dimensions and conversion of units

The height of mercury column in a barometer in a Calcutta laboratory was recorded to be 75 cm. Calculate this pressure in SI and CGS units using the following data : specific gravity is 13.6, density of water is 1000 kg/m3, g is 9.8 m/s2 at Calcutta. Pressure = hρg in usual symbols Your email:

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## Current electricity – Numerical

A 10m length of aluminium wire has a diameter of 1.5mm. It carries a current of 12A. Find (i) the current density. (ii) the drift velocity (iii) the electric field in the wire. aluminium has approximately 10^29 free electrons per m^3

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## A numerical problem on Drift velocity

Two conducting wires X and Y of same diameter but different materials are joined in series across a battery . if the number density of electrons in X is twice that in Y . Find the ratio of drift velocity of electrons in the two wires. (Adithya Singh asked this) Incoming search terms:i want to […]

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## Dimensional Analysis – A solved example

Deduce the dimensional formula for workdone,pressure and density. [posted by boineelo ] Answer: workdone We know that workdone = force x distance Therefore [work done] =  [force] [distance] but force = ma [force]=[m][a] [a]=[velocity]/[t] [velocity]=[displacement]/[t] So, putting all these together [work done]=[m][distance][distance]/[time][time] [work done]=ML2T-2 Similarly, you can work out the dimensional formula for pressure and density as [pressure]=[force]/[area]=ML-1T-2 […]

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## Explanation For Empirical Horopter: Density Of Photoreceptors

Karolis  asks: ” External SiteLink -In this website (and in many more) in page 5, it’s written that photoreceptors are more densely packed in nasal areas of retina than temporal. That’s one of the explanations why empirical horopter (that’s the unit of all points in visual field, that are seen in the same position monocularly) […]

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## Solution to HC Verma Q-21 of chapter 30

Neha posted this question: “Two large conducting plates are placed parallel to each other with a sepration of 2.00cm between them. an electron starting from rest near one of the plates reaches the other plate in 2.00 microseconds. find the surfac…