Inertia affects the flow of water pumped through a closed system of

Question

Inertia affects the flow of water pumped through a closed system of pipes. When the pump is first switched on, the water, which has mass, takes time to reach full speed. When the pump is switched off, inertia causes the decrease in the water flow to be gradual. The effects of inductance in electrical circuits are similar to the effects of inertia in water pipes.

The information above provides the most support for which one of the following?

A. The rate at which electrical current flows is affected by inductance

B. The flow of electrical current in a circuit requires inertia

C. Inertia in the flow of water pumped by an electrically powered pump is caused by inductance in the pump's circuit

D. Electrical engineers try to minimize the effects of inductance in electrical circuits

E. When a water pump is switched off it continues to pump water for a second or two

pqhai · Accepted Answer

Good question. A is correct.

First of all, this is  “MUST BE TRUE”  question. The most important thing of this type of question is  “ NO NEW  information accepted” . A correct answer MUST pass the “Fact test”. 
There are only  2 types of correct answer :
 (1) Paraphrase  (re-write parts of the stimulus in other way but keep the same meaning)
 (2) Combination  (combine two or more parts of the stimulus to make an inference)

ANALYZE THE STIMULUS:

Fact #1:  Inertia affects the flow of water pumped through a closed system of pipes
 Fact #2:  The pump is on, inertia causes the mass water takes time to reach full speed. 
 Fact #3:  The pump is off, inertia causes the decrease in the water flow to be gradual.
 Fact #4:  The effects of inductance in electrical circuits are similar to the effects of inertia in water pipes.

ANALYZE EACH ANSWER:

A. The rate at which electrical current flows is affected by inductance 
  Correct.    This is a combination of fact#1 and fact#4:  flow of water is affected by inertia; inductance affects electrical flows in the similar way as inertia does ==> Flow of electrical current is affected by inductance.

B. The flow of electrical current in a circuit requires inertia
 Wrong.  “Flow of electrical current is affected by inductance, not inertia”; In addition, “require” differs from “affects” ==> out immediately

C. Inertia in the flow of water pumped by an electrically powered pump is caused by inductance in the pump's circuit
 Wrong.  No direct link between “inertia in the flow of water” and “inductance in pump’s circuit” ==> Out immediately.

D. Electrical engineers try to minimize the effects of inductance in electrical circuits
 Wrong.  Nothing about “engineers try to minimize the effect of inductance” ==> Out immediately.

E. When a water pump is switched off it continues to pump water for a second or two
 Wrong.   SHELL GAME . Fact #3 just says: inertia causes the decrease in the water flow to be gradual. Thus, E is wrong because:
(1) The stimulus  does not mention how long  a water pump continues to pump. 
(2) You  cannot infer  “decrease in the water flow to be gradual” = 1 or 2 seconds.  It may be 3 seconds, or even a minutes,  who knows?

TAKEAWAY:

In "Must be true" question:
(1) No new info accepted.
(2) A correct answer MUST pass the fact test.

Hope it helps.

fameatop · Answer

Inertia affects the flow of water pumped through a closed system of pipes. When the pump is first switched on, the water, which has mass, takes time to reach full speed. When the pump is switched off, inertia causes the decrease in the water flow to be gradual. The effects of inductance in electrical circuits are similar to the effects of inertia in water pipes. 
The information above provides the most support for which one of the following?
A. The rate at which electrical current flows is affected by inductance  - Correct 
 
B. The flow of electrical current in a circuit requires inertia 
 - We know that inductance effects flow of current in electrical circuits but we don't know whether circuit requires inertia or not. Incorrect

C. Inertia in the flow of water pumped by an electrically powered pump is caused by inductance in the pump's circuit 
 - Nowhere it's mentioned What causes Inertia. This option assumes that inductance causes inertia but such assumption is not justified. Incorrect

D. Electrical engineers try to minimize the effects of inductance in electrical circuits
 - We don't know whether Inductance results in positive or negative effect & to assume that Inductance results in Negative effect is unjustified. Incorrect.

E. When a water pump is switched off it continues to pump water for a second or two 
 - Very close contender but it may be that when a water pump is switched off it continues to pump water only for 1 MILLI second. Incorrect.

Argod · Answer

Lets proceed option wise

A. Try to negate this option and u see the argument falls apart,seems a good option, hold this one.

B. This one is mixing two different phenomena/terms..so can be easily eliminated.

C. Same as B

D. Out of scope

E. This one is a close contender, but is too specific and falls on the logical aspect..it could be very well possible that the water continues to flow for 3 secs or maybe half a second..the time duration for which the water continues to flow cannot be determined.

Hence, A is the correct answer.

BeckyRobinsonTPR · Answer

This is an inference question so the correct answer must be something that can be proven true based soley on the facts in the argument. In this case we know:
1) Inertia affects the flow of water pumped in a closed system
2) a pump takes some time to reach full spead adn some time to completely decrease the flow of water.
3) Inductance effects electrical circuits in a similar way to how inertia affects pumps.
 
 We know the decrease happens gradually, but we do not know the actual time frame of the decrease

docdrizzeally · Answer

Another new forma introduction. This question would have been considered inelegant by the previous generation as it leaves yous half way. Inductance actually does not affect flow of current per se but as the aragraph mentions adds a delay to the initial flow and a delay after switching off during which the current peters down to 0

pjaseem · Answer

Hi, Doesnt Answer A bring in outside information.The Initial Paragraph does not even talk about electric current at all.It says the inductance affects circuits the same way as the mass of water.It doesnt say that the inductance affects the "current flowing" .Is this question correct?

plumber250 · Answer

Hi Pjaseem,

I'm not sure you're correct. Here is how I break down the paragraph, and I'll show where I think the answer (A) becomes logical...

Inertia affects the flow of water pumped through a closed system of pipes.  This is the initial statement - the main point if you will

When the pump is first switched on, the water, which has mass, takes time to reach full speed. When the pump is switched off, inertia causes the decrease in the water flow to be gradual.  This is simply an explanation of the initial statement - it's 'fluff' we don't actually need to understand it to answer the question.

The effects of inductance in electrical circuits are similar to the effects of inertia in water pipes.  This is a comparison to the iniital statement.

SO - we have 2 statements, the second being compared to the first. Looked at in this way we can see that A, logically follows the comparison. Because inertia affects flow, we know inductance is similar to inertia, so it makes sense that inductance affects flow as well

James

ramannanda9 · Answer

I do not agree with option a 
It says that inductance affects the rate of electric current flow, but inductance does not actually limit or increase the rate after the initial delay or before the final pause.

pjaseem · Answer

Hi Plumber250, I agree Inductance affects the flow of something as per the passage.That something could be " voltage " for all we know (yes an engineer would find that stupid! :shock:

). The paragraph never talks about "current" or "flow of current" in circuits. Aren't we bringing in outside information ? :!:

Gian · Answer

Analogy used in the last sentence : The effects of inductance in electrical circuits are similar to the effects of inertia in water pipes. Now, the effects of inertia in water pipes are as follows: a) When power is on, rate of water is increased. b) When power is off, rate of water is decreased. So, its logical to conclude that inertia is affecting the rate of water flowing through the pipes. Similarly, inductance will affect the rate of current flowing through the electrical circuits. Moreover, current only seems logical to infer to flow through the circuits,for electrons and other sub-atomic particles would be too scientific terms

rishabhmudgal · Answer

IMO A... Option D cant be the answer as the stimulus is saying that the speed of water flow decreases after pump is switched off... nothing is said about the decrease in water passing through the pump. So D is out of scope.

nightblade354 · Answer

Bumping for discussion. Not a hard LSAT question, but one that can help you pay attention!

Gladiator59 · Answer

1 min 30 sec

Inertia affects the flow of water in pipes -> effects of  inductance in electrical circuits  are similar to the effects of  inertia in water pipes  ->  therefore    inductance must affect the flow of electricity in circuits

If you have any confusion about "  the rate at which  " - this part is confirmed by the description of what happens when a pump is switched on & off. 
Since we have been given that inductance in circuits is analogous to inertia in water pipes, if inertia is affecting the rate at which water flows - inductance must also affect the rate at which electricity flows. This is exactly what is given by the lines "When the pump is first switched on, the water, which has mass, takes time to reach full speed. When the pump is switched off, inertia causes the decrease in the water flow to be gradual." Thus inertia definitely affects the rate of flow of water.

Best,
Gladi

egmat · Answer

Passage Analysis 
Inertia affects the flow of water pumped through a closed system of pipes.
  Inertia is something that affects the flow of water through a system of pipelines that are closed on the whole.

When the pump is first switched on, the water, which has mass, takes time to reach full speed.
 When the machine that pumps water through the pipes is started, the water current experience a delay in reaching its maximum speed since water has mass.

When the pump is switched off, inertia causes the decrease in the water flow to be gradual.
When the pump is turned off. Inertia causes the reduction in speed of the water current to have a time delay too.

The last two statements explain how inertia exerts an influence on water flow in pipes.
 
The effects of inductance in electrical circuits are similar to the effects of inertia in water pipes.
The flow of water through pipes is compared to the flow of electricity through a circuit. The author states that what inertia does to the water current is what inductance does to electric current.

Question stem 
The information above provides the most support for which one of the following?
  It asks for the statement which is most supported by the passage. This is an inference question.

Thought Process 
Any statement that re-iterates the given information in the passage
OR
Any statement that combines two or more different pieces of information in the passage
OR 
Any statement that is the logical antecedent of the information given in the passage will form a correct inference.

Option Analysis 
 A. The rate at which electrical current flows is affected by inductance  
 Correct. If water current is affected by inertia as statements 2&3 say and electric current is analogous to water current with inductance playing the role of inertia, then electric current flow must be affected by inductance. There is no need of any subject specific knowledge to reach this inference.

B. The flow of electrical current in a circuit requires inertia
 Incorrect. It is not inertia that affects electric current but its electricity counterpart inductance, according to the passage.

C. Inertia in the flow of water pumped by an electrically powered pump is caused by inductance in the pump's circuit.
 There is no information provided about the pump's circuit or the relation between inductance in that circuit to the inertia of water. All we know to affect the inertia is the mass of water. Therefore, incorrect choice.

D. Electrical engineers try to minimize the effects of inductance in electrical circuits
 Incorrect. What electrical engineers try to do does not come under the scope of the passage. It only deals with the parallels in the effects of inertia and inductance on water currents and electric currents.

E. When a water pump is switched off it continues to pump water for a second or two
 This cannot be inferred from the passage. All we know is that once the pump is off, the inertia of water does not allow to stop flowing instantly even when the pump is not forcing it to flow.

egmat · Answer