If you stand up in a big room and echo, your voice will echo
from the walls. As long as the room is empty. Since
the speed of sound is constant, depending on air density, the more humid the
air the faster and farther sound travels. The
speed of sound is constant, you could measure the time it takes for your voice
to echo off the walls. The same thing happens with Doppler radar, but it’s not voice,
it has higher frequency signals.<span> </span>
A boiling pot of water (the water travels in a current throughout the pot), a hot air balloon (hot air rises, making the balloon rise) , and cup of a steaming, hot liquid (hot air rises, creating steam) are all situations where convection occurs.
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Answer:
Current through each phase Vp = 2.2A
Total three phase power Pt= 1.45kW
Power factor of the load pf = 1
Explanation:
i) Find current through each phase
Vp =220V (rms)
Z =100 Ω
I = Vp/Z
= 220/100
= 2.2A
ii) Find the total three phase power
for a resistive load, Power, P = VI
Power for each phase is given as:
P = 220 * 2.2
= 484 W
Total power TP =3* P
=484*3
= 1452W
=1.45kW
iii) Find the power factor of the load
Phase angle for a resistive load is 0.
α= 0
Hence, power factor of load = cos α
pf = cos 0
pf = 1
Answer: The hottest star is Archenar( blue) and the coolest star is Betelgeuse
Explanation:
Objects emit radiation that depends exclusively on their temperature. At an ambient temperature, the radiation emitted by an object is in the infrared spectrum (we could only see it with a special camera). If we heat it we will see that it first turns red (whose state we call “red hot”) because it is the lowest and least energetic wavelength of all.
If we continue to heat it, the wavelength that it emits to one with more energy will continue to increase and we will see that it turns yellow and then white. This is a signal that is emitting at all frequencies (but mainly in blue).
If we continue to warm a body that is "white hot", it would emit in the ultraviolet spectrum, with what would become ... black! then we would not see it emits light in the visible spectrum (well, we would see a very faint bluish light corresponding to the tail of the distribution of the spectrum it emits, but the peak of that spectrum would be in the ultraviolet).
