# Two rails and a rod (magnetic field)

1. Jan 28, 2007

### lalala_land89

1. The problem statement, all variables and given/known data
Two stiff parallel wires a distance L apart in a horizontal plane act as rails to support a light metal rod of mass m(perpendicular to each rail). A magnetic field B, directed out of the page(textbook page) acts throughtout. At t=0 , wires connected to the rails are connected to a constant current-source and a current I begins to flow through the system. East to the bottom rail, north to the rod , west to the upper rail. Determine the speed of the rod as a function of time a) assuming there's no friction b) there's friction cofficient U c) In which direction does the rod move, east or west , if the current through it is north?

2. Relevant equations

a) x=vt ??????????????? b) mechanical equaction Ffr= U Fn ??????? c) west

I'm lost with this. help plz.

2. Jan 30, 2007

### siddharth

Why do you think that is the answer? Do you have any thoughts/ideas on how to approach this problem?

3. Jan 30, 2007

### Meir Achuz

The force on the wire is ILB. Then apply F=ma.

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