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3 years ago

What role does density play in the movement of convection curruents?

Physics

1 answer:

shtirl [24]3 years ago

7 0

Convection occurs through heat transfer due to a difference in density in the fluids.

Consider a pot of water being heated. The water in the pot gets heated rises ,it provides energy for the particles in the water to move and thus the water expands which results in the density of the water becoming less. These particles rise up till the top of the pot owing to the property of very less density of the particles.

Then after some time, it cools down which results in increase of the density of the particles. The heavier denser particles sink to the bottom and is once again heated and rises and this process continues unless all the water particles in the pot are heated and warmed.This transfer of energy by the movement of particles cause convection.

During the day the heat surface above the earth exposed to the sun's rays is heated. This rise in temperature,decreases the density of the air and the warm air rises.

This air cools down and becomes denser. This dense cool air sink back and forces the warm air to rise again.

This transfer of movement of particles causes convection. This cycle is the cause of winds and thus energy is transferred through the atmosphere.

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A student switches the torch on and sees that it gives out a bright light.

garik1379 [7]

Answer:

no more fire duhh

Explanation:

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2 years ago

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Suppose a scoentist was able to construct a barometer with a liquid being denser than mercury , then how high would the liquid r

ki77a [65]

Answer:

the liquid has less height than the mercury

h_{ liquid} = $\frac{\rho_{Hg} }{\rho_{liqid}} \ h_{Hg}$

Explanation:

The pressure as a function of the height is given by

P = ρ g h

where ρ is the density of the liquid, g the acceleration of gravity and h the height reached by the column of the liquid

In that case they say that the pressure is the standard one that is P = 1.01 10⁵ Pa = 760 mmHg

The first way to give the pressure is in SI units and the second way is the height that the mercury column reaches

In the case of building a barometer with a liquid that has a density greater than that of mercury

ρ_liquid > ρ_Hg

the pressure

P =ρ_lquid g h_liquid

if we have the same pressure

ρ_{Hg} g h_{Hg} = ρ_{liquid} g h_{liquid}

h_{ liquid} = $\frac{\rho_{Hg} }{\rho_{liqid}} \ h_{Hg}$

therefore the liquid has less height than the mercury

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3 years ago

Consider a semi-infinite (hollow) cylinder of radius R with uniform surface charge density. Find the electric field at a point o

VikaD [51]

Answer:

For the point inside the cylinder: $E = \frac{\sigma R}{2\epsilon_0}\frac{1}{\sqrt{R^2 + 4x_0^2}}$

For the point outside the cylinder: $E = \frac{\sigma R}{2\epsilon_0}\frac{1}{\sqrt{R^2 + x_0^2}}$

where x0 is the position of the point on the x-axis and σ is the surface charge density.

Explanation:

Let us assume that the finite end of the cylinder is positioned at the origin. And the rest of the cylinder lies on the (-x) axis, which is the vertical axis in this question. In the first case (inside the cylinder) we will calculate the electric field at an arbitrary point -x0. In the second case (outside), the point will be +x0.

The cylinder is consist of the sum of the rings with the same radius.

First we will calculate the electric field at point -x0 created by the ring at an arbitrary point x.

We will also separate the ring into infinitesimal portions of length 'ds' where ds = Rdθ.

The charge of the portion 'ds' is 'dq' where dq = σds = σRdθ. σ is the surface charge density.

Now, the electric field created by the small portion is 'dE'.

$dE = \frac{1}{4\pi\epsilon_0}\frac{\sigma Rd\theta}{R^2+x^2}$

The electric field is a vector, and it needs to be separated into its components in order us to integrate it. But, the sum of horizontal components is zero due to symmetry. Every dE has an equal but opposite counterpart which cancels it out. So, we only need to take the component with the sine term.

$dE = \frac{1}{4\pi\epsilon_0}\frac{\sigma Rd\theta}{R^2+x^2} \frac{x}{\sqrt{x^2+R^2}} = dE = \frac{1}{4\pi\epsilon_0}\frac{\sigma Rxd\theta}{(R^2+x^2)^{3/2}}$

We have to integrate it over the ring, which is an angular integration.

$E_{ring} = \int{dE} = \frac{1}{4\pi\epsilon_0}\frac{\sigma Rx}{(R^2+x^2)^{3/2}}\int\limits^{2\pi}_0 {} \, d\theta = \frac{1}{4\pi\epsilon_0}\frac{\sigma Rx}{(R^2+x^2)^{3/2}}2\pi = \frac{1}{2\epsilon_0}\frac{\sigma Rx}{(R^2+x^2)^{3/2}}$

This is the electric field created by a ring a distance x away from the point -x0. Now we can integrate this electric field over the semi-infinite cylinder to find the total E-field:

$E_{cylinder} = \int{E_{ring}} = \frac{\sigma R}{2\epsilon_0}\int\limits^{-\inf}_{-2x_0} \frac{x}{(R^2+x^2)^{3/2}}dx = \frac{\sigma R}{2\epsilon_0}\frac{1}{\sqrt{R^2 + 4x_0^2}}$

The reason we integrate over -2x0 to -inf is that the rings above -x0 and below to-2x0 cancel out each other. Electric field is created by the rings below -2x0 to -inf.

We will only change the boundaries of the last integration.

$E_{cylinder} = \int{E_{ring}} = \frac{\sigma R}{2\epsilon_0}\int\limits^{-\inf}_{x_0} \frac{x}{(R^2+x^2)^{3/2}}dx = \frac{\sigma R}{2\epsilon_0}\frac{1}{\sqrt{R^2 + x_0^2}}$

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3 years ago

A fan connected to a 120-volt electrical system by an extension cord was worn through and exposed the bare, energized conductor,

kari74 [83]

Answer: the ladder

Explanation: since the energized conductor is already in contact with the ladder there by making electric current to flow. The base of the ladder is on the ground there by making the circuit to be complete and causing electrocution.

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2 years ago

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If there is no gravity what will happen to earth?

Serga [27]

Wouldn't everything fall?

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3 years ago

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