Magnetic Induction Problem

1. Mar 20, 2006

Dr.Brain

Ok there are two plastic rails over which a metal wire is kept , the wire is kept prependicular to both plastic rails , over the rails.. The coefficient of friction is 'n' between the metal and the plastic . The mass of the plastic wire is 'm' , Calculate the magnitude of the Magnetic field B , which just allows the wire to move.

I equate dthe net frictional force which will try to limit the motion , with the Magnetic force given by ILB , but in the answer instead of 'n' . there is some square root fuction of 'n'in the denominator and n in the numerator. , please help.

2. Mar 20, 2006

Chi Meson

The wire will feel no force at all unles there is a current going through it. What information do you have about the current in this wire? I'm assuming this is not a magnetic wire (not iron or cobalt)?

3. Mar 20, 2006

Dr.Brain

ok the current in the wire is 'i' .

4. Mar 20, 2006

Chi Meson

I assume there is also an "L" given. In that case you are exactly right. B=('n'mg)/(IL)

5. Mar 21, 2006

Dr.Brain

but the answer is given to be : nmg / (IL)[sqrt(1+n(^2)]

6. Mar 21, 2006

Chi Meson

What level of physics is this? High school or college, and is it calculus based? Are you using differential equations?

I can not think of any reason why increasing the coefficient of friction should decrease the required magnetic field to start moving an object by the lorentz force. This is either an advanced, peculiar property I don't know about, or a mistake.

ANyone else want this one?

Last edited: Mar 21, 2006
7. Mar 21, 2006

Dr.Brain

I am in my first year at a tech-school , and this is Physics-II which we r taught in the second semester , but I think it doesnt matter what level i am studing , i just need to solve the problem. Use calculus or whatever .

8. Mar 21, 2006

Chi Meson

I've looked in six college textbooks, and I can't find any reference to that peculiar formula. Sorry, but I'm done here