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3 years ago

True or False All objects emit electromagnetic waves.

Physics

1 answer:

MariettaO [177]3 years ago

7 0

Answer:

true

explanations: especially hot body ie.above -273 tends to emit infrared type radiation

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A TV set shoots out a beam of electrons. The beam current is 10A. How many electrons strike the TV screen in a minute.

Wittaler [7]

Answer:

600 mC

Explanation:

The charge of an electron is 1.6 x 10-19C so for a current with 10 mA, the charge going to screen in one second is 10 mC

so number of electrons, n = (10 x 10-3)/(1.6 x 10-19) = 6.25 x 1016 so in a minute the charge is 10 * 60 = 600 mC

4 0

3 years ago

Read 2 more answers

Water evaporating from a pond does so as if it were diffusing across an air film 0.15 cm thick. The diffusion coefficient of wat

QveST [7]

Answer:

The water level will drop by about 1.24 cm in 1 day.

Explanation:

Here Mass flux of water vapour is given as

$j_{H_2O}=\frac{D}{l} \bigtriangleup c$

where

$j_{H_2O}$ is the mass flux of the water which is to be calculated.

D is diffusion coefficient which is given as $0.25 cm^2/s$

l is the thickness of the film which is 0.15 cm thick.
$\bigtriangleup c$ is given as

$\bigtriangleup c= \frac{P_{sat}-P_a}{RT}$

In this

$P_{sat}$ is the saturated water pressure, which is look up from the saturated water property at 20°C and 0.5 saturation given as 2.34 Pa

$P_a$ is the air pressure which is given as 0.5 times of $P_{sat}$

R is the universal gas constant as $8.314 kJ/kmol-K$

T is the temperature in Kelvin scale which is $20+273= 293K$

By substituting values in the equation

$\bigtriangleup c= \frac{P_{sat}-P_a}{RT} \\ \bigtriangleup c= \frac{P_{sat}-0.5P_{sat}}{RT} \\ \bigtriangleup c= \frac{0.5P_{sat}}{RT} \\ \bigtriangleup c= \frac{0.5 \times 2.34}{8.314 \times 293} \\\bigtriangleup c= 0.48 mol/m^3$

Converting $\bigtriangleup c$ into $cm^3/cm^3$

As 1 mole of water 18 $cm^3$ so

$\bigtriangleup c= 0.48 mol/m^3 \\ \bigtriangleup c= 0.48 \times 18 \times 10^{-6} cm^3/cm^3 \\ \bigtriangleup c= 8.64 \times 10^{-6} cm^3/cm^3$

Putting this in the equation of mass flux equation gives

$j_{H_2O}=\frac{D}{l} \bigtriangleup c \\ j_{H_2O}=\frac{0.25}{0.15} \times 8.64 \times 10^{-6} \\ j_{H_2O}=14.4 \times 10^{-6} cm/s$

For calculation of water level drop in a day, converting mass flux as

$j_{H_2O}=14.4 \times 10^{-6} \times 24 \times 3600 cm/day\\ j_{H_2O}=1.24 cm/day$

So the water level will drop by about 1.24 cm in 1 day.

7 0

4 years ago

Which of the following is a category of mechanical wave?

givi [52]

Answer:

because the mechanical wave is when it goes over and over again

8 0

3 years ago

Read 2 more answers

Why is external fertilization not possible in organisms that live on land

Softa [21]

because the sperm and the egg will dry out

4 0

3 years ago

What two types of energy does a rock have as it rolls down a hill

AnnZ [28]

Kinetic energy

When the rock starts rolling down the hill it has kinetic energy. When the rock gets to the bottom of the hill and stops, it is no longer in motion therefore it no longer has kinetic energy, the energy has been converted back into potential energy.

3 0

3 years ago