Edexcel physics: Confusing Question! Help, anyone?

12

I am confused about a physics question.
It says
In which wire will the electrons have a greater drift velocity- a thick wire or a thin wire?

My initial thought was that a thick wire would have a greater drift velocity, because of its larger cross sectional area, but then I thought about the equation I = nAvq
Rearranging would give v = I/nAq This indicates that the cross sectional area is inversely proportional to the drift velocity, which doesn’t make sense to me.

Can anyone help? Am I completely missing something?

Reply 1

mathematician

scarlet ibis

I am confused about a physics question.
It says
In which wire will the electrons have a greater drift velocity- a thick wire or a thin wire?

My initial thought was that a thick wire would have a greater drift velocity, because of its larger cross sectional area, but then I thought about the equation I = nAvq
Rearranging would give v = I/nAq This indicates that the cross sectional area is inversely proportional to the drift velocity, which doesn’t make sense to me.

Can anyone help? Am I completely missing something?

the thin wire will have a greater drift velocity,

Reply 2

mathematician

the thin wire will have a greater drift velocity,

what dont u understand ?

Reply 3

vp03

i tried doing it with imaginary numbers but i too got confused. With I, n, and e the same and Area varied, i got 8 then doubled the area and got 4. wudnt the drift velocity be higher if the area was doubled? someone explain this

Reply 4

vp03

mathematician

the thin wire will have a greater drift velocity,

why the thin one?

Reply 5

gzftan

12

scarlet ibis

I am confused about a physics question.
It says
In which wire will the electrons have a greater drift velocity- a thick wire or a thin wire?

My initial thought was that a thick wire would have a greater drift velocity, because of its larger cross sectional area, but then I thought about the equation I = nAvq
Rearranging would give v = I/nAq This indicates that the cross sectional area is inversely proportional to the drift velocity, which doesn’t make sense to me.

Can anyone help? Am I completely missing something?

No..that's right..i know it sounds odd..but that's the way it works...thin wires have greater drift velocity.

Odd isn't it....don't worry..you don't need to understand why...just know how to work it out from the formula

G

Reply 6

mathematician

scarlet ibis

I am confused about a physics question.
It says
In which wire will the electrons have a greater drift velocity- a thick wire or a thin wire?

My initial thought was that a thick wire would have a greater drift velocity, because of its larger cross sectional area, but then I thought about the equation I = nAvq
Rearranging would give v = I/nAq This indicates that the cross sectional area is inversely proportional to the drift velocity, which doesn’t make sense to me.

Can anyone help? Am I completely missing something?

ill try ne explaing, u can see from the equation I=nAqV, I is proprtional to the area yer?, so there fore the thicker wire will have a large current.
ok, the thinner wire has to have the same current, as the thicker wire, so the only other variable u can change is the dift velocity.
for the thick wire, A is high, V is low, and for the thin wire A is low and V is high, they both compensate, do u get it?

Reply 7

The Albatross

OP

12

ok thanx
so the thinner wire will have a greater drift velocity to compensate for its small x-sectional area. right?
so if i just use the formula to explain it, i should be ok?

Reply 8

mathematician

scarlet ibis

ok thanx
so the thinner wire will have a greater drift velocity to compensate for its small x-sectional area. right?
so if i just use the formula to explain it, i should be ok?

yup u got it, just write down the formula and explain it

Reply 9

The Albatross

OP

12

cool thank you mathematician and gzftan! :biggrin:

Edexcel physics: Confusing Question! Help, anyone?

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