In a cyclotron, charged particles, or ions, are accelerated inside an

Question

In a cyclotron, charged particles, or ions, are accelerated inside an evacuated tank, to prevent them from colliding with air molecules and being scattered. The vacuum tank is placed between the poles of an electromagnet, which creates a field that bends the ion beam into a circular orbit between two accelerating electrodes, or “dees.” Because the ions carry a positive electric charge, they are attracted toward the dee, which is electrically negative at the moment. Were it not for the magnetic field, the ions would be accelerated in a straight line; instead, they are deflected into a circular path back toward the dee gap. By the time the ions again reach the dee gap, the sign of the electric potential on the dees is reversed, so that now the ions are attracted toward the opposite dee. As this process of alternating the electric potential is repeated, the ions gain speed and energy with each revolution. This causes them to spiral outward in a  regular  manner. Finally, they strike a target inserted into their path or are extracted from the cyclotron for use as an external beam.    1 
 1. Based on the information presented in the passage, which of the following most closely represents the sequence of events describing the path of an ion in a cyclotron?

A. A positively charged ion is repelled from a negative dee, then attracted to a positive dee.
B. A negatively charged ion is attracted to a positive dee, then repelled by a negative dee.
C. A positively charged ion is attracted to a negative dee, then attracted by a magnetic field.
D. A positively charged ion is attracted to a negative dee, then attracted to a negative dee.
E. A positively charged ion is attracted to a negative dee, which reverses the ion’s electric potential.

2 
 2. In the context in which it appears, “regular” most nearly means

A. normal
B. agreeable
C. average
D. predictable
E. useful

3 
 3. The author of the passage mentions the magnetic field primarily in order to

A. argue that the magnetic field is less important than the dee gap in cycling the ions
B. suggest that ions would accelerate to dangerous speeds without a magnetic field
C. provide support for the notion that, in nature, ions tend to travel in straight lines
D. cast doubt on the hypothesis that ions tend to travel elliptically once deflected
E. indicate the necessity of deflecting the ions back toward the dee gap

agrotechpepper · Answer

Any OE? Because I am confused with all the OAs especially Q1 but also Q2,Q3 seems confusing

Sajjad1994 · Answer

Official Explanation

1. Based on the information presented in the passage, which of the following most closely represents the sequence of events describing the path of an ion in a cyclotron?

The passage explains that the ions, which are positive, are attracted to the negative dee, then again attracted to a negative dee after the dee’s electric potential has been reversed. 
 
  Answer: D

Sajjad1994 · Answer

Official Explanation

2. In the context in which it appears, “regular” most nearly means

It can be inferred from the context that the author believes that the ions in the cyclotron act in a predictable way because their behavior is described chronologically and authoritatively; the author therefore uses  “regular”  to mean  “predictable.”  
 
  Answer: D

Sajjad1994 · Answer

Official Explanation

3. The author of the passage mentions the magnetic field primarily in order to

The author explains the magnetic field as a tool with which to direct the ions back toward the dee gap; he is therefore indicating the necessity of that direction for the operation of the cyclotron. 
 
  Answer: E

agrotechpepper · Answer

But why not C? The author is also mentioning the nature of the ion to move in straight line thus magnetic field is introduced. Kindly help in explaining where I am thinking wrong. Thanks.

egmat · Answer

I understand why option C seems appealing - you've correctly identified that the passage mentions ions traveling in straight lines without the magnetic field. This is a classic GMAT trap answer that tests your ability to distinguish between  primary purpose  and  supporting details .

Why E is Correct (Not C):
 
The key is understanding the  hierarchical structure  of the information presented:

Main Purpose of the Passage:  Explain how a cyclotron works 
  Role of Magnetic Field:  Essential component that enables the cycling mechanism 
  Supporting Detail:  Ions would travel straight without the magnetic field

When the author states  "Were it not for the magnetic field, the ions would be accelerated in a straight line; instead, they are deflected into a circular path back toward the dee gap,"  this isn't meant to  prove  that ions naturally travel straight. Rather, it's explaining  why the magnetic field is necessary  for the cyclotron to function.

Critical Distinction:

Option C suggests:    The author's goal is to support/prove a scientific principle about ion behavior  
  Option E recognizes:  The author's goal is to explain the magnetic field's functional necessity in the cyclotron's operation

The "Primary Purpose" Test:  Ask yourself:  If I removed this information, would the passage still achieve its goal? 
 
 Without explaining the magnetic field's role in deflecting ions back to the dee gap, the cyclotron's mechanism remains unexplained ✗ 
 Without proving ions travel straight naturally, the cyclotron explanation still works ✓  
 
Strategic Takeaway for RC Questions:  When asked about why an author mentions something "primarily," always connect it to the passage's  overall purpose , not to interesting side facts mentioned along the way. GMAT frequently uses true statements from the passage as wrong answers when they're not the  primary  reason for including that information.

The magnetic field isn't mentioned to teach us about ion physics - it's mentioned because without it, the cyclotron simply wouldn't work. The ions  must  be deflected back to continue the acceleration cycle.

In a cyclotron, charged particles, or ions, are accelerated inside an

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GMAT Reading Comprehension (RC) Questions

In a cyclotron, charged particles, or ions, are accelerated inside an

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