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14 Nov 2019, 08:30
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Question 1
B
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
89% (03:05) correct
11%
(03:29) wrong
based on 421
sessions
History
Date
Time
Result
Not Attempted Yet
Question 2
C
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
68% (01:15) correct 32%
(01:11) wrong
based on 474
sessions
History
Date
Time
Result
Not Attempted Yet
Question 3
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
21% (01:47) correct 79%
(01:35) wrong
based on 462
sessions
History
Date
Time
Result
Not Attempted Yet
Question 4
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
5%
(low)
Question Stats:
77% (00:56) correct 23%
(01:12) wrong
based on 428
sessions
History
Date
Time
Result
Not Attempted Yet
Question 5
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
54% (01:31) correct 46%
(01:28) wrong
based on 426
sessions
History
Date
Time
Result
Not Attempted Yet
New Project RC Butler 2019 - Practice 2 RC Passages Everyday
Passage # 451, Date: 14-Nov-2019
This post is a part of New Project RC Butler 2019. Click here for Details
Passage # 451, Date: 14-Nov-2019
This post is a part of New Project RC Butler 2019. Click here for Details
Subatomic particles can be divided into two classes: fermions and bosons, terms coined by physicist Paul Dirac in honor of his peers Enrico Fermi and Satyendra Bose. Fermions, which include electrons, protons, and neutrons, obey the Pauli exclusion principle, according to which no two particles can inhabit the same fundamental state. For example, electrons cannot circle the nuclei of atoms in precisely the same orbits, loosely speaking, and thus must occupy more and more distant locations, like a crowd filling seats in a stadium. The constituents of ordinary matter are fermions; indeed, the fact that fermions are in some sense mutually exclusive is the most salient reason why two things composed of ordinary matter cannot be in the same place at the same time.
Conversely, bosons, which include photons (particles of light) and the hitherto elusive Higgs boson, do not obey the Pauli principle and in fact tend to bunch together in exactly the same fundamental state, as in lasers, in which each photon proceeds in perfect lockstep with all the others. Interestingly, the seemingly stark division between fermionic and bosonic behavior can be bridged. All particles possess “spin,” a characteristic vaguely analogous to that of a spinning ball; boson spins are measured in integers, such as 0 and 1, while fermion spins are always halfintegral, such as ½ and 1½. As a result, whenever an even number of fermions group together, that group of fermions, with its whole-number total spin, effectively becomes a giant boson. Within certain metals chilled to near absolute zero, for instance, so-called Cooper pairs of electrons form; these pairs flow in precise harmony and with zero resistance through the metal, which is thus said to have achieved a superconductive condition. Similarly, helium-4 atoms (composed of 2 electrons, 2 protons, and 2 neutrons) can collectively display boson-like activity when cooled to a superfluid state. A swirl in a cup of superfluid helium will, amazingly, never dissipate.
The observation that even-numbered groups of fermions can behave like bosons raises the corollary question of whether groups of bosons can ever exhibit fermionic characteristics. Some scientists argue for the existence of skyrmions (after the theorist Tony Skyrme who first described the behavior of these hypothetical fermion-like groups of bosons) in superconductors and other condensed-matter environments, where twists in the structure of the medium might permit skyrmions to form.
Conversely, bosons, which include photons (particles of light) and the hitherto elusive Higgs boson, do not obey the Pauli principle and in fact tend to bunch together in exactly the same fundamental state, as in lasers, in which each photon proceeds in perfect lockstep with all the others. Interestingly, the seemingly stark division between fermionic and bosonic behavior can be bridged. All particles possess “spin,” a characteristic vaguely analogous to that of a spinning ball; boson spins are measured in integers, such as 0 and 1, while fermion spins are always halfintegral, such as ½ and 1½. As a result, whenever an even number of fermions group together, that group of fermions, with its whole-number total spin, effectively becomes a giant boson. Within certain metals chilled to near absolute zero, for instance, so-called Cooper pairs of electrons form; these pairs flow in precise harmony and with zero resistance through the metal, which is thus said to have achieved a superconductive condition. Similarly, helium-4 atoms (composed of 2 electrons, 2 protons, and 2 neutrons) can collectively display boson-like activity when cooled to a superfluid state. A swirl in a cup of superfluid helium will, amazingly, never dissipate.
The observation that even-numbered groups of fermions can behave like bosons raises the corollary question of whether groups of bosons can ever exhibit fermionic characteristics. Some scientists argue for the existence of skyrmions (after the theorist Tony Skyrme who first described the behavior of these hypothetical fermion-like groups of bosons) in superconductors and other condensed-matter environments, where twists in the structure of the medium might permit skyrmions to form.
B
(A) explain the mechanism by which fermions can become bosons
(B) describe the two classes of subatomic particles
(C) provide examples of the different forms of matter
(D) explain the concept of particle “spin”
(E) argue that most matter is composed of one type of particle
C
(A) They can be composed of groups of fermions.
(B) They are measured in integer spin.
(C) They are the constituents of ordinary matter.
(D) They tend to bunch together in the same fundamental state.
(E) They lead to phenomena such as superconductors and superfluids.
D
(A) An atom composed of two protons and a neutron would be considered a boson.
(B) Skyrmions have been discovered in superconductors and other condensed matter environments.
(C) Two electrons in an atom cannot circle the same nucleus at exactly the same distance.
(D) A current through a superconducting wire will never dissipate.
(E) Fermions cannot behave as bosons unless they are cooled to a temperature near absolute zero.
A
(A) Fermions cannot inhabit the same fundamental state, whereas bosons bunch together in the same state.
(B) Fermions contain many more types of particles than bosons.
(C) Fermions exist in groups, but bosons do not.
(D) Fermions have integral spin values, whereas Bosons have half-integer spin.
(E) Fermions do not obey the Pauli principle, whereas bosons do.
A
(A) Fermi Energy: The maximum energy that electrons in a solid will contain in order to avoid having identical energy levels
(B) Particle Accelerators: Devices that will accelerate charged particles to very high speeds through the application of an external magnetic field
(C) Quantum Entanglement: When particles interact physically and then become separated but still have interdependent properties
(D) Double Slit Experiment: An experiment that revealed the particle and wave duality of photons
(E) The Higgs Field: The field produced by the conjectured Higgs particle that would explain why matter has mass
365/1904
15 Nov 2019, 07:45
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need explanation for q3. Why the answer should not be C??
15 Nov 2019, 08:06
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Hea234ven
Official Explanation
3. Which of the following can be properly inferred from the passage?
Difficulty Level: Hard
Explanation
The second paragraph states that Cooper pairs of electrons will “flow in precise harmony and with zero resistance through the metal.” As an example of the same phenomenon, the second paragraph also states that a “swirl in a cup of superfluid helium will, amazingly, never dissipate.” Therefore, it is correct to infer that “a current through a superconducting wire will never dissipate,” as in choice (D).
As for (A), the passage states that an even number of fermions (which, according to the first paragraph, “include electrons, protons, and neutrons”) constitute a boson, but not an odd number (½ integer times an odd will not give an integer).
The last paragraph states that “scientists argue for the existence of skyrmions” in a medium that might permit them to be formed, implying that they have not yet been discovered, so eliminate (B).
In (C), the author states that two electrons cannot circle a nucleus in the same orbit, but they could spin in different orbits that are the same distance from the nucleus.
Finally, in (E), the author gives two examples of fermions becoming bosons at cooled temperatures but does not say this is the only situation in which this can occur.
Answer: D
Difficulty Level: Hard
Explanation
The second paragraph states that Cooper pairs of electrons will “flow in precise harmony and with zero resistance through the metal.” As an example of the same phenomenon, the second paragraph also states that a “swirl in a cup of superfluid helium will, amazingly, never dissipate.” Therefore, it is correct to infer that “a current through a superconducting wire will never dissipate,” as in choice (D).
As for (A), the passage states that an even number of fermions (which, according to the first paragraph, “include electrons, protons, and neutrons”) constitute a boson, but not an odd number (½ integer times an odd will not give an integer).
The last paragraph states that “scientists argue for the existence of skyrmions” in a medium that might permit them to be formed, implying that they have not yet been discovered, so eliminate (B).
In (C), the author states that two electrons cannot circle a nucleus in the same orbit, but they could spin in different orbits that are the same distance from the nucleus.
Finally, in (E), the author gives two examples of fermions becoming bosons at cooled temperatures but does not say this is the only situation in which this can occur.
Answer: D
Hope it helps
