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Effectus [21]
3 years ago
11

Which device is using a motor? A. A water heater creates heat energy from electric energy. B. A waterfall rotates a waterwheel t

o turn an axle. C. A body massager uses electric energy to move back and forth. D. A solar charger creates electric energy from the Sun.
Physics
1 answer:
Mumz [18]3 years ago
4 0

Answer:

C is the right answer.

Body massager uses electrical energy to move back and forth. In this sense, a motor is being used for the operation

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Find the electron and hole mobilities, and the resistivity of intrinsic silicon at 300K. Is intrinsic silicon a semiconductor
tino4ka555 [31]

Answer:

Resistivity = 231.481 K Ohm

Yes, Intrinsic Silicon is the semiconductor.

Explanation:

Solution:

At 300K:

Let suppose mobility of electron in intrinsic semiconductor = M_{e}

Mobility of electron in intrinsic semiconductor is:

M_{e}  = 1300 cm^{2}/volt.sec

Let suppose mobility of hole in intrinsic semiconductor = M_{h}

M_{h} = 500 cm^{2}/volt.sec

We know that, intrinsic silicon semiconductor has equal number of holes and electrons. So,

At 300 K

Intrinsic Carrier Concentration = 1.5 x 10^{10}/cm^{3} = C

And,

Conductivity of intrinsic Silicon is:

σ = C x (M_{h} + M_{e}) e

e = 1.6 x 10^{-19} C

So, plugging in the values, we get:

σ = C x (M_{h} + M_{e}) e

σ = 1.5 x 10^{10} x (500 + 1300) x 1.6 x 10^{-19}

σ = 4.32 x 10^{-6}

So, now we can find the resistivity.

Resistivity = 1/σ

Resistivity = 1/ 4.32 x 10^{-6}

Resistivity = 231.481 K Ohm

Yes, Intrinsic Silicon is the semiconductor.

7 0
3 years ago
Why do the planets appear in different locations in the night sky while the pattern of stars in a constellation stays the same?
Goshia [24]
I'm sure you've noticed that an airplane high in the sky, far away
from you, looks like it's moving very slowly.  At the same time,
somebody passing you on a skateboard whizzes past you at
high speed.  The farther away something is from you, the slower
it appears to move.

The nearest star outside the solar system is almost 32 thousand times
as far away from us as the farthest visible planet (Saturn) is, and all of the
other stars are farther than that. 

That's why you have to wait a few thousand years before you notice
that the shape of a constellation has changed.

To put it a slightly different way . . . Everything is in motion.  The motion is
more noticeable for nearby things, and less noticeable for farther-away things. 
Objects within our solar system are the only ones near enough so that a human
lifetime is a long enough period in which to notice the change in their position.
Even Pluto moves less then 1.5° against the 'background' stars in a whole year.

This all makes me feel small.  How about you ?
7 0
3 years ago
Read 2 more answers
A charge of Q is fixed in space. A second charge of q was first placed at a distance r1 away from Q. Then it was moved along a s
topjm [15]

Answer:

\Delta U = \frac{Qq}{4\pi\epsilon_0}(\frac{1}{r_2^2}-\frac{1}{r_1^2})

Explanation:

The electrostatic potential energy is given by the following formula

U = \frac{1}{4\pi\epsilon_0}\frac{q_1q_2}{r^2}

Now, we will apply this formula to both cases:

U_1 = \frac{1}{4\pi\epsilon_0}\frac{Qq}{r_1^2}\\U_2 = \frac{1}{4\pi\epsilon_0}\frac{Qq}{r_2^2}

So, the change in the potential energy is

\Delta U = U_2 - U_1 = \frac{Qq}{4\pi\epsilon_0}(\frac{1}{r_2^2}-\frac{1}{r_1^2})

7 0
3 years ago
A rocket achieves a lift-off velocity of 500.0 m/s from rest in 30.0 seconds. Calculate the average acceleration of the rocket.
Anettt [7]

Answer:

The average acceleration is 16.6 m/s² ⇒ 1st answer

Explanation:

A rocket achieves a lift-off velocity of 500.0 m/s from rest in

30.0 seconds

The given is:

→ The initial velocity = 0

→ The final velocity = 500 meters per seconds

→ The time is 30 seconds

Acceleration is the rate of change of velocity of the rocket

→ a=\frac{v-u}{t}

where a is the acceleration, v is the final velocity, u is the initial velocity

and t is the time

→ u = 0 , v = 500 m/s , t = 30 s

Substitute these values in the rule

→ a=\frac{500-0}{30}=\frac{500}{30}=16.6 m/s²

<em>The average acceleration is 16.6 m/s²</em>

6 0
3 years ago
Compare and contrast between reflection and refraction
Tcecarenko [31]

Differences:

<u>Reflection</u> is described as the reverting back of light or sound waves in the same medium, when it falls on plane.

<u>Refraction</u> means the shift in direction of the radio waves, when it enters medium with different density.

Comparisons:

<u>Reflection and refraction</u> <em>both</em> change the direction of light and both <em>do not </em>absorb light. All light waves can be reflected and refracted.

Both <u>Reflection and Refraction</u> are phenomenon related with wave motion of sound, and electromagnetic waves, thus including light.

3 0
3 years ago
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