# Charge carrier drift velocity of wire

• ravsterphysics
In summary: Vx is equivalent to 2 parts of Vy. Then Vx:Vy should be 1:2 because 1 part of Vx is equivalent to 2 parts of Vy.
ravsterphysics

## The Attempt at a Solution

Current is I = nqvA so drift velocity V is: V = I/nqA

Drift velocity for x is: Vx = I/nqA

Drift velocity for y is: Vy = 2I/nqA

So the ratio of Vx : Vy should be 2:1 since Vy is equal to 2 lots of Vx?? (but correct answer is B)

ravsterphysics said:
So the ratio of Vx : Vy should be 2:1 since Vy is equal to 2 lots of Vx?? (but correct answer is B)
You may want to rethink your logic there.

Edit: My mistake. I presumed that their table presented the ratios as ##V_y:V_x##, but looking again at the text I see that it's the other way around. So the book's suggested answer is incorrect as you found.

Edit2: I retract my retraction! See later postings.

Last edited:
ravsterphysics said:

## Homework Statement

View attachment 111644

## The Attempt at a Solution

Current is I = nqvA so drift velocity V is: V = I/nqA

Drift velocity for x is: Vx = I/nqA

Drift velocity for y is: Vy = 2I/nqA

So the ratio of Vx : Vy should be 2:1 since Vy is equal to 2 lots of Vx?? (but correct answer is B)

gneill said:
You may want to rethink your logic there.

Edit: My mistake. I presumed that their table presented the ratios as ##V_y:V_x##, but looking again at the text I see that it's the other way around. So the book's suggested answer is incorrect as you found.

nickyfernandezzz said:

I've done this question a few times now and ended up with the same answer, but the question is from an official exam paper in the UK so I don't believe there's been a mistake.

FYI, here's what the mark scheme says:

How can it still be B?

I'm retracting my edit from before. Clearly the coffee isn't working this morning

If the cross sectional area is halved the velocity doubles. So Vy is twice Vx as you originally pointed out:
ravsterphysics said:
since Vy is equal to 2 lots of Vx
So ##V_y## is twice the size of ##V_x##. That makes the ratio ##V_x:V_y = 1:2## which is indeed answer B.

gneill said:
I'm retracting my edit from before. Clearly the coffee isn't working this morning

If the cross sectional area is halved the velocity doubles. So Vy is twice Vx as you originally pointed out:

So ##V_y## is twice the size of ##V_x##. That the ratio ##V_x:V_y = 1:2## which is indeed answer B.

Indeed. Vy/2=Vx , so Vx: Vy should be 1:2 because then Vy÷2=1.

gneill said:
I'm retracting my edit from before. Clearly the coffee isn't working this morning

If the cross sectional area is halved the velocity doubles. So Vy is twice Vx as you originally pointed out:

So ##V_y## is twice the size of ##V_x##. That makes the ratio ##V_x:V_y = 1:2## which is indeed answer B.

nickyfernandezzz said:
Indeed. Vy/2=Vx , so Vx: Vy should be 1:2 because then Vy÷2=1.
Vx = I/nqA

and

Vy = 2[I/nqA] = 2Vx

so doesn't that mean that for every 1 part of Vx we have half a part of Vy? So that 2 parts of Vx gives 1 part of Vy so the ratio is still C, 2:1?? Argh!

Pick a value for the magnitude of Vx, say 1. What value would you assign to Vy using your expressions?

ravsterphysics said:
Vx = I/nqA

and

Vy = 2[I/nqA] = 2Vx

so doesn't that mean that for every 1 part of Vx we have half a part of Vy? So that 2 parts of Vx gives 1 part of Vy so the ratio is still C, 2:1?? Argh!

2Vx=Vy. So , if the value of Vx is 1, value of Vy should be 2 right?

nickyfernandezzz said:
2Vx=Vy. So , if the value of Vx is 1, value of Vy should be 2 right?
Right. So, Vx = 1, Vy = 2. What's Vx:Vy?

gneill said:
Right. So, Vx = 1, Vy = 2. What's Vx:Vy?

Then Vx:Vy should be 1:2

## 1. What is charge carrier drift velocity and how is it related to wire?

Charge carrier drift velocity is the average speed at which free electrons move through a wire. It is related to wire because it is a measure of the flow of electric current through a wire.

## 2. How is charge carrier drift velocity calculated?

Charge carrier drift velocity is calculated by dividing the electric current in the wire by the number of charge carriers and the cross-sectional area of the wire. It can also be calculated using the formula v = I/(nAq), where v is the drift velocity, I is the electric current, n is the number of charge carriers, A is the cross-sectional area, and q is the charge of the carrier.

## 3. What factors affect charge carrier drift velocity in a wire?

The charge carrier drift velocity in a wire can be affected by several factors, including the material of the wire, the temperature of the wire, the strength of the electric field, and the density of charge carriers in the wire.

## 4. Why is charge carrier drift velocity important in electrical circuits?

Charge carrier drift velocity is important in electrical circuits because it determines the rate at which electric current flows through a wire. It also affects the resistance of the wire, which can impact the efficiency and performance of the circuit.

## 5. How does charge carrier drift velocity differ in different types of wires?

Charge carrier drift velocity can vary depending on the material and properties of the wire. For example, in a metal wire, the free electrons have a higher drift velocity compared to a semiconductor wire. Additionally, the temperature and density of charge carriers can also affect the drift velocity in different types of wires.

• Introductory Physics Homework Help
Replies
11
Views
394
• Introductory Physics Homework Help
Replies
4
Views
2K
• Introductory Physics Homework Help
Replies
10
Views
2K
• Introductory Physics Homework Help
Replies
9
Views
2K
• Introductory Physics Homework Help
Replies
6
Views
11K
• Introductory Physics Homework Help
Replies
29
Views
7K
• Introductory Physics Homework Help
Replies
14
Views
2K
• Introductory Physics Homework Help
Replies
2
Views
1K
• Introductory Physics Homework Help
Replies
13
Views
2K
• Introductory Physics Homework Help
Replies
1
Views
2K