Particle flow in wires of same current but diff diameter?

In summary: The Attempt at a SolutionI chose B because since current is equal in both wires, I thought that the rate of charge flow is equal. Isn't that the definition of current?? Apparently I'm wrong since the answer is D. How can this be?the resistance of a wire depends on it's cross section. the smaller the cross section, the higher the resistance. if the resistance is higher, you need a higher voltage to produce the same current. that's why the answer is D...none of these answers are really satisfactory...the resistance of a wire depends on it's cross section. the smaller the cross section, the higher the resistance. if the resistance is higher, you need a higher voltage to produce the same current
  • #1
toforfiltum
341
4

Homework Statement


upload_2015-7-23_23-20-45.png


Homework Equations


I=Q/t

The Attempt at a Solution


I chose B because since current is equal in both wires, I thought that the rate of charge flow is equal. Isn't that the definition of current?? Apparently I'm wrong since the answer is D. How can this be?
 
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  • #2
the resistance of a wire depends on it's cross section. the smaller the cross section, the higher the resistance. if the resistance is higher, you need a higher voltage to produce the same current. that's why the answer is D...none of these answers are really satisfactory...
 
  • #3
cpsinkule said:
the resistance of a wire depends on it's cross section. the smaller the cross section, the higher the resistance. if the resistance is higher, you need a higher voltage to produce the same current. that's why the answer is D...none of these answers are really satisfactory...
But won't the higher voltage be offset by the higher resistance, since I=V/R?
 
  • #4
the current is the same in both wires, if the resistance goes up, the only way for that equation to remain true is if the voltage goes up as well
 
  • #5
cpsinkule said:
the current is the same in both wires, if the resistance goes up, the only way for that equation to remain true is if the voltage goes up as well
So does that mean that the charged particles will move faster through the wire?
 
  • #6
yes, the net amount of charge passing through one point in the wires is proportional to the area of the wire and the speed of the electrons. both of these have equal current so that a smaller area requires a larger velocity to produce the same current
 
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  • #7
Maybe D is the correct answer, but it's a weird way of thinking.

Instead think of an hourglass whre sand is flowing through a narrow hole. Where in the hourglass will the sand flow fastest? At the biggest/smallest cross section area?
And why?
 
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  • #8
cpsinkule said:
yes, the net amount of charge passing through one point in the wires is proportional to the area of the wire and the speed of the electrons. both of these have equal current so that a smaller area requires a larger velocity to produce the same current
Ah, I see, so to confirm, to produce the same amount of charge flowing through a smaller cross-sectional area per unit time, the velocity of the particles must be higher, right?
 
  • #9
that's the idea
 
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  • #10
Hesch said:
Maybe D is the correct answer, but it's a weird way of thinking.

Instead think of an hourglass whre sand is flowing through a narrow hole. Where in the hourglass will the sand flow fastest? At the biggest/smallest cross section area?
And why?
Wow, nice question, though I'm not sure about the answer.:biggrin: I suppose it should be at the smallest cross-sectional area, since it's at point of lowest pressure? Add also, rate of flow must be equal everywhere, so to make up for the smaller cross-sectional area, the sand there must flow faster...but what I say seems contradictory...
 

Related to Particle flow in wires of same current but diff diameter?

1. What is particle flow in wires?

Particle flow in wires refers to the movement of charged particles, such as electrons, through a wire in response to an electric current. As electrons flow through a wire, they transfer energy and create an electric current.

2. How does the diameter of a wire affect particle flow?

The diameter of a wire affects particle flow in two main ways. First, a larger diameter wire allows for more particles to flow through it, as there is more space for them to move. Second, a larger diameter wire has less resistance, meaning that particles can flow more easily.

3. What is the relationship between current and particle flow in wires of different diameters?

The relationship between current and particle flow in wires of different diameters is directly proportional. This means that as the current increases, the number of particles flowing through the wire also increases. And as the diameter of the wire increases, the amount of current that can flow through it also increases.

4. How does temperature affect particle flow in wires of the same current but different diameters?

Temperature can affect particle flow in wires of the same current but different diameters in a few ways. First, as temperature increases, the resistance of the wire also increases, which can decrease the amount of current flowing through the wire. Second, a higher temperature can cause the particles themselves to move more quickly, increasing the overall flow of particles in the wire.

5. What are some practical applications of understanding particle flow in wires of the same current but different diameters?

Understanding particle flow in wires of different diameters is important for many practical applications. It is used in the design of electrical circuits and systems, as well as in the production of various electronic devices. It is also essential for understanding and optimizing the efficiency of power transmission and distribution systems.

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