## Magnetic field question?

1. The problem statement, all variables and given/known data

The conductive bar CD with a length of 20 cm and resistance R, moves with speed v=5 m/s. The magnetic field is perpendicular with the plan and the induction is B=2 T.
The mass of the object in the figure is m=80 grams and g=10 m/ s^2
a) find the direction and the intensity of the induced current that moves in CD
b) The resistance of this bar

2. Relevant equations

Figure : http://s1171.photobucket.com/albums/...rent=hrtfg.jpg

3. The attempt at a solution
I tried using Emf=B*L*v and then I=emf/R but i dont know the R..
I JUST WANT TO KNOW HOW TO RELATE Tension and weight with induction//
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 If the bar is moving at a constant speed this tells you something about the resultant force on the bar? There is a force due to the weight of the mass and there is a force due to any induced current flowing in the wire CD.
 Hello Elaia06, You have to find the induced current first which as truesearch points out bases itself on the fact that the rod is moving at a constant velocity.Tension can be found out basing your derivations on the same fact.Direction of induced current comes out as a result of the same(analyse the forces on the rod and see which direction of current corresponds to equilibrium).Then for resistance you have adequate expressions in your attempt . regards Yukoel

## Magnetic field question?

Ah, the resultant force is zero.This means the only force acting on the bar is the magnetic force F=B*i*l.
Now we have the Tension= mg-ma but acceleration is zero so we write
Magnetic force = Force on the string
B*i*l=m*g
I know how to solve this now
The magnetic force will have the direction <---- based on the figure and the induced current the direction from left to right .

IS IT CORRECT NOW?
 Blog Entries: 27 Recognitions: Gold Member Homework Help Science Advisor you haven't used v or R
 after i find I, then I use I=b*L*v/R and so I find R :) Is it correct in total?
 Blog Entries: 27 Recognitions: Gold Member Homework Help Science Advisor yes, that's correct
 Thank you very much sweetheart! :D