Fundamentals of Astronomy and Physics: Key Concepts
Fundamentals of Astronomy and Physics
4. The frequency of a wave is:
- All of the above
5. You are standing on Earth’s equator. Where is Polaris?
- On the northern horizon
6. Which of the following statements about scientific models is true?
- A model can be used to explain and predict real phenomena.
7. The energy attributed to an object by virtue of its motion:
- Kinetic energy
8. Which of the following statements is NOT true about scientific theories?
- A theory cannot be taken seriously by scientists if it contradicts
Cosmic Evolution: From the Big Bang to Dark Energy
The Future of the Universe
Cosmologists believe that the future of the universe depends on the density of its mass-energy. Two possible scenarios were initially considered: the Big Chill and the Big Crunch. However, the recent discovery of dark energy, responsible for the accelerating expansion, has introduced another possibility: the Big Rip.
- Big Chill: The Great Cooling. An open universe where matter-energy is insufficient to reach critical density, allowing gravity-free expansion.
- Big Crunch: The
Understanding Magnetism: Permanent, Ferro, Para, and Diamagnetic Materials
Understanding Magnetism
Permanent Magnet: Once magnetized, remains magnetized.
Ferromagnet: Easily magnetized (iron, nickel, cobalt, some rare-earth metals, magnetite).
Paramagnet: Magnetized with more difficulty.
Diamagnet: Repels magnetic fields (slightly) – “not magnetic”.
Materials are broken into smaller chunks called “domains”. Each domain has a miniature magnetic field.
Domain Differences
Even if materials look the same, at a smaller level their domains could be different – hence why some
Read MoreThermodynamics: Entropy, Coefficients, and Ideal Gases
Thermodynamics
Entropy
In a Carnot cycle, the integral of Q1/T1 from 0 to Q2/T2 equals 0, where T1 and T2 are the temperatures. This gives us Q1/T1 + Q2/T2 = 0. Considering ΔQ = at, we have at1/T1 + at2/T2 = 0, thus ∑ ΔQ/T = 0.
Now, for a cyclic transformation, ∑ ΔQ/T = ∫1a2 ΔQ/T + ∫2b1 ΔQ/T = 0. If we consider other ways of reasoning, ∫1N2 ΔQ/T, the ratio of heat transfer at different temperatures is a constant. This magnitude is called Entropy.
The third principle of thermodynamics
Read MoreUnderstanding Faraday’s and Ampere’s Laws in Electromagnetism
Faraday’s Law of Electromagnetic Induction
Faraday’s Law expresses the induced electromotive force (EMF) as a function of the variation of magnetic flux (ΦB):
EMF = – ΔΦB / Δt
The electromotive force induced in a coil is equal to the rate of change of the magnetic flux through the surface bounded by the loop. For a coil with N turns, the EMF induced is:
EMF = -N * (ΔΦB / Δt)
If the coil has tightly wound turns, the flux through each turn will be the same, and the EMF induced in the coil is the
Read MoreAcoustic Physics: Sound Wave Properties and Phenomena
Acoustic Physics: Sound Wave Properties
Elongation: The distance between the point of balance and the position of particles at a given time.
Amplitude: The distance between the highest point and the point of equilibrium, similar to elongation. (Higher energy results in greater amplitude)
Period: The time it takes a particle to complete one vibration.
Frequency: The number of times an event is repeated within a given time. Specifically, the number of vibrations performed in 1 second.
Wavelength: The distance
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