Velocity of electron at the end of a contraction

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Homework Help Overview

The problem involves the velocity of an electron as it moves from a region with a cross-sectional area A to a region with a larger cross-sectional area of 2A. The original poster presents multiple options regarding the relationship between the initial and final velocities of the electron.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relationship between current densities in the two sections and how they might relate to the velocities of the electrons. There are questions about the adequacy of the information provided and the relevance of concepts from current electricity.

Discussion Status

The discussion is ongoing, with participants exploring the implications of charge carriers and current flow in different cross-sectional areas. Some guidance has been offered regarding the analogy of electron flow to water flow in pipes, prompting further inquiry into the behavior of electrons in varying conductor sizes.

Contextual Notes

There is a noted lack of knowledge about current electricity among some participants, which may affect their ability to engage fully with the problem. The original poster expresses concern about insufficient information to reach a conclusion.

randomgamernerd
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Homework Statement

:[/B]
Velocity of an electron at point A1 is Vo where cross sectional area is A. The velocity of electron at the end of contraction at point B where cross sectional area is 2A is V1.Find correct option

a)V1< V0
b)V1= V0
c)V1> V0
d)V1<=V0/2
I have attached a picture of the question as well.
Please refer to it for the diagram.
(Question 9)
image.jpg


Homework Equations

: I failed to relate it with electrostatics

The Attempt at a Solution

:[/B]
I feel the given information is insufficient to determine the answer.
something about the charge of the cross sectional area or atleast something more should have been mentioned.

 
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How are the current densities related between the two sections? What about the current itself?
 
kuruman said:
How are the current densities related between the two sections? What about the current itself?
I don't know...I have not learned current electricity yet
 
randomgamernerd said:
I don't know...I have not learned current electricity yet
OK, then let's talk about charge carriers. You have two conductors one narrower than the other. Electrons flow through them like water molecules in a pipe under pressure. You are at a fixed point on the narrow conductor and count how many electrons per second pass before you. Your friend does the same thing on the wide conductor. Answer these two questions and you will see what's going on.
1. Who counts more electrons per second?
2. Given your previous answer, who sees electrons move by more quickly?
 

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