Consider the system pictured in the figure below. A 15.7-cm horizontal wire of m

Question

Consider the system pictured in the figure below. A 15.7-cm horizontal wire of mass 16.2 g is placed between two thin, vertical conductors, and a uniform magnetic field acts perpendicular to the page. The wire is free to move vertically without friction on the two vertical conductors. When a 4.90-A current is directed as shown in the figure, the horizontal wire moves upward at constant velocity in the presence of gravity. (a) What forces act on the horiontal wire? (Selec al that apply.) magnetic force electric force gravitational force (b) Under what condition is the wire able to move upward at constant velocity? This answer been graded yet (c) Find the magnitude and direction of the minimum magnetic tield required to move the wire at constant speed magnitude

Explanation / Answer

a) the magnetic force and the force of gravity.

b) when the magnetic force is upward and balances the

downward force of gravity , the net force on the wire is zero

and so there will not be any acceleration so the wire can move upwards at constant velocity.

c) magnetic force F = BIL sin

from this ,magnetic field is
          B = F/(IL sin) (since , force F =mg)

              = mg/(IL sin)

= (16.2*10-3 kg)(9.8 m/s2) /((4.9 A)(15.7*10-2 m)(sin90))

              = 0.206 T

Direction of magnetic field can be determined by right hand rule,

stretch right hand palm such that thumb points in the direction of current and normal to palm is along force, then the fingers will be in direction of field.

direction : out of the page

d) when the magnetic field exceeds the value we obtained , the net upward force will increase , thereby the wire accelerates upward.

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