Parallel wires question (1 Viewer)

[wrxsti]

Two long parallel wires carry current in the same direction. The force between the wires has magnitude F . The seperation between wires is halved while the current in each wire is doubled. The force between the wires is now???

the Answer is Magnetude 8F and attractive

i understand the magnitude part... but why are the wires attrative.... the current is flowing in the same direction doesnt that mean that the wires are repulsive.... can someone explain this please :S

 

[alcalder]

Actually, currents in the same direction cause attraction. It is currents in the opposite direction that cause repulsion. This is opposite from magnet NOrth and South.

You can think of it this way.

Conside a current carrying wire in the magnetic field of another wire. Let's assume the current is upwards in BOTH wires.

There is a left and right wire.

Using the grip rule, the magnetic field around the right-hand wire is out of the page where the left-hand wire is.

Now, use the left hand rule on the left-hand wire.

The magnetic field is out of the page, the current is up the page and so the force on this wire is towards the other wire.

(There are lots of left and rights there, I hope you got it. Draw yourself a diagrom of it.)
Hope that helps

 

[wrxsti]

thanx yer it does help... this module is killing me. :S

 

[xiao1985]

/bows to alcalder

A truly splendid explanation, deserves and applause.

 

[thehootman]

Its really not that hard..... but anyway

 

[xiao1985]

Its really not that hard..... but anyway

build your reputation as a physics god, and i shall bow to you too.

for now, you are a commoner.

 

[BlackJack]

No, xiao, that's no way to treat your younger compatriots.

 

[xiao1985]

No, xiao, that's no way to treat your younger compatriots.

i agree...

i had been bit of a dick there =/

i was mad as he was mocking (intentionally or unintentionally) a student's desire for knowledge...

 

[thehootman]

Her answer was similar to one that could be found in a multitude of text books... and your reply sounded as if she had explained the meaning of life in one sentence, in which case I can understand "bowing". If it was an answer to a hard question, I could understand your reply, but alas it was not a hard question (i dont mind people asking easy questions).