Remember Dark Energy is repulsive, the more the faster the universe expands (indeed accelerates), so the faster it would cool down and increase its size, not the other way. Now, no one knows what it is. For instance, if Dark Energy would rather be some other geometric effect, it could have a different ending than just if it is a cosmological constant term. So far, though, all experimental data do not favor anything else that is not compatible with just a cosmological constant ... We'll need to wait few years (~10 years) to get to know much better this with missions and ground experiments that are undergoing or planned to be launched.
transformer makes use of mutual induction for its operation in which change in magnetic field in one coil due to variation of current , induces voltage in the other coil. so changing magnetic field in the primary coil is very much needed for the transformer. Alternating current is a current which varies with time , hence it is suitable to produce changing magnetic field in the primary coil. on the other hand , the direct current remains constant all the time. hence can not produce a changing magnetic field. so DC current is not useful for transformers.
It tells us the number of protons that are present in the nucleus, the positively charged region of that atom.
Answer:
b) Betelgeuse would be 
times brighter than Sirius
c) Since Betelgeuse brightness from Earth compared to the Sun is 
the statement saying that it would be like a second Sun is incorrect
Explanation:
The start brightness is related to it luminosity thought the following equation:
(1)
where 
is the brightness, 
is the star luminosity and 
, the distance from the star to the point where the brightness is calculated (measured). Thus:
b) 
and 
where 
is the Sun luminosity (
) but we don't need to know this value for solving the problem. 
is light years.
Finding the ratio between the two brightness we get:
c) we can do the same as in b) but we need to know the distance from the Sun to the Earth, which is 
. Then
Notice that since the star luminosities are given with respect to the Sun luminosity we don't need to use any value a simple states the Sun luminosity as the unit, i.e 1. From this result, it is clear that when Betelgeuse explodes it won't be like having a second Sun, it brightness will be 5 orders of magnitude smaller that our Sun brightness.
The peak magnetic field of the electromagnetic wave in the red part of the visible spectrum is 9.67 x 10⁻¹⁰ T.
<h3>Relationship between electric and magnetic field</h3>
The relationship between electric and magnetic field at a given peak electric field is given as;
c = (E₀) / (B₀)
where;
- c is speed of light
- E₀ is the peak electric field
- B₀ is the peak magnetic field
B₀ = E₀ / c
B₀ = (2.9) / (3 x 10⁹)
B₀ = 9.67 x 10⁻¹⁰ T
Thus, the peak magnetic field of the electromagnetic wave in the red part of the visible spectrum is 9.67 x 10⁻¹⁰ T.
Learn more about peak magnetic field here: brainly.com/question/24487261
