Saturday, August 15, 2009

Ørsted Google Doodle physics question

See the Google Doodle in the post below. Assume that current is flowing through the copper wire and that the painted (red) end of the compass needle seeks north.

What is the direction of conventional current in the wire?
A. from the G to the e
B. from the e to the G

Defend your answer.


stevieray said...

e to G

Apply the Right-hand-current rule in the section of the Google Wire directly underneath the compass with thumb pointed to the Left and curling fingers going into the plane of the page away from the viewer. Compass needle aligns following the direction of the curvature of the fingers.
P.S. - If this is incorrect, apply the left-hand-current rule and reverse everything I wrote above including that "e to G" bit.

Dean Baird said...

"the section of the Google Wire directly underneath the compass"

Stevie Ray Deux said...

should have said "below" the compass - at least from my view. The wire is not really directly over the face of the compass though this would NOT change my original answer (unless of course you're left handed)

Dean Baird said...

My right hand tells me the current travels from G to e. Grab that stretch of wire spanning the compass with your thumb to the right. Below the wire (where the compass is), fingers point away(ish) from us, in agreement with the compass needle. If the compass were moved above (atop) the wire, the compass would reverse polarity.

This may have to be settled with a Thumb War. Is there an app for that?

stevieray said...

Try downloading "I Thumb My Nose At You!" - latest iPhone APP from Nares Inc.

stevieray said...

You're right Ye Bard of Baird: G -to -e it is. It looked to me like the compass was more above the wire than below it in the Google Doodle.
Do I sense a free-verse response perturbing the Ether?

Dean Baird said...

I think I've done quite enough to drive off both my blog's readers.

Converter said...

I guess its from G to e.but the picture is not clear.