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usatkling
Dec8-04, 12:03 AM
I have a question. Please help

A wire having a linear mass of 1 g/cm is place on a horizontal surface that has a kinetic coefficient of friction of 0.2 . The wire carries a current of 1.5Amps toward the East, which is to the right of this page, and slide horizontally to the North , which is the top of this page. What are the magnitude and direction of the smallest magnetic field that enables the wire to move in this manner?

maverick280857
Dec8-04, 12:41 AM
Welcome to PF usatkling!

What are the forces acting on the body? Its weight, the normal reaction from the surface, a Lorentz Force and a friction force. Their resultant will cause the body to accelerate unless their resultant is zero.

usatkling
Dec8-04, 11:16 PM
I still didn't get it. It make no sense. There is no electric field involve here. The question is how to relate The external magetic field B to the current of the wire.
I know the resultant force in the moving need to be equal to the friction force

Phymath
Dec8-04, 11:43 PM
all u have to do is set the force of friction equal to the force equation between to magnetic fields in two wires, i can't think of the formula right now but im sure u can find it.

the friction should be uN, which is (.2)(mg)-> (.2)((1 g/cm)*L g) where L is length of the wire

maverick280857
Dec9-04, 09:14 PM
The Lorents Force on a conductor of length L carrying a current I when placed in a uniform magnetic field B is given by

\vec{F}=I(\vec{L}X\vec{B})