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3 years ago

15

A teacher wants to demonstrate that unheated water can boil at room temperature in a beaker within a bell jar connected to a vac

-uum pump. However, the vacuum pump is faulty and can reduce pressures only to 15 kPa. Can the teacher use this pump to perform the demonstra-tion successfully? Explain your answer.

1 answer:

laiz [17]3 years ago

8 0

Answer:

No .

Explanation:

The vapor pressure of water at room temperature is .0313 atom or 3.13 kPa.

To make a liquid boil, its vapor pressure must be equal to pressure around it.

So pump must create pressure of 3.13 k Pa or less to make water attain its stage of boiling at room temperature. As the motor can not produce pressure lesser than 15 k Pa , pump will not be able to make water boil at room temperature.

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Rahim is watching his favorite football team on television. In order to work, the television must be

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Answer:

it would be the cord will have the most energy at the moment.

Explanation:

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3 years ago

Can electromagnetic waves travel in a vacuum? <br><br> Yes <br> Or<br> No

Sonja [21]

Answer:

Yes

Explanation:

Yes because Electromagnetic waves differ from mechanical waves in that they do not require a medium to propagate. This means that electromagnetic waves can travel not only through air and solid materials, but also through the vacuum of space.

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2 years ago

Azurite is a mineral that contains 55.1% of copper. How many meter of copper wire with diameter of 0.0113 in can be produced fro

soldier1979 [14.2K]

Answer:

1402.73 m

Explanation:

Mass of Azurite=3.25 lb

Percent of copper in AZurite mineral=55.1%

Diameter of copper wire,d=0.0113 in

Radius of copper wire= $r=\frac{d}{2}=\frac{0.0113}{2}=0.00565 in=\frac{565}{100000}=\frac{565}{100}\times \frac{1}{1000}=5.65\times 10^{-3}in$

$\frac{1}{1000}=10^{-3}$

Density of copper= $\rho=8.96g/cm^3$

1 lb=454 g

3.25 lb= $3.25\times 454=1475.5 g$

Mass of Azurite= $1475.5 g$

Mass of copper= $\frac{55.1}{100}\times 1475.5=813 g$

Density= $\frac{Mass}{volume}$

Using the formula

$8.96=\frac{813}{volume\;of\;copper}$

Volume of copper wire= $\frac{813}{8.96}=90.7cm^3$

Radius of copper wire= $5.65\times 10^{-3}\times 2.54=14.35\times 10^{-3} cm$

1 in=2.54 cm

Volume of copper wire= $\pi r^2 h$

$\pi=3.14$

Using the formula

$90.7=3.14\times (14.35\times 10^{-3})^2\times h$

$h=\frac{90.7}{3.14\times (14.35\times 10^{-3})^2}$

$h=140273 cm$

1 m=100 cm

$h=\frac{140273}{100}=1402.73 m$

Hence, the length of copper wire required=1402.73 m

7 0

3 years ago

A solenoidal inductor for a printed circuit board is being redesigned. To save weight, the number of turns is reduced by one-fif

AlladinOne [14]

The "it must be five times larger" current change if the energy stored in the inductor is to remain the same.

<u>Explanation:</u>

A current produced by a modifying magnetic field in a conductor is proportional to the magnetic field change rate named INDUCTANCE (L). The expression for the Energy Stored, that equation is given by:

$U= \frac{1}{2} LI^2$

Here L is the inductance and I is the current.

Here, energy stored (U) is proportional to the number of turns (N) and the current (I).

$L = \frac{\mu_0 N^2 *A}{l}$

mu not - permeability of core material

A -area of cross section

l - length

N - no. of turns in solenoid inductor

Now,given that the proportion always remains same:

$\frac{N_2}{N_1} = \frac{I_1}{I_2}$

In this way the expression

$\frac{1}{5} = \frac{I_1}{I_2}$

$I_2 = I_1 \times 5$

Thus, it suggest that "it must be five times larger" current change if the energy stored in the inductor is to remain the same.

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3 years ago

A stone is thrown vertically upwards with an initial velocity of 20m/s. Find the maximum height it reaches and the time taken by

ruslelena [56]

Answer:

20m in 2 secs

Explanation:

t=2s

s=20m

hence the maximum height reached by stone is 20m in 2 s

5 0

3 years ago