Consider the system pictured in the figure below. A16.1-cm horizontal wire of ma
ID: 2199813 • Letter: C
Question
Consider the system pictured in the figure below. A16.1-cm horizontal wire of mass16.4g 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 a5.05-A current is directed as shown in the figure, the horizontal wire moves upward at constant velocity in the presence of gravity.
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magnitude T direction ---Select---out of the screeninto the screenupleftrightdownExplanation / Answer
Part A: forces acting on the horizontal wire include: magnetic and gravitational force. Part B: When the magnetic force is upward and balances the downward gravitational force, the net force on the wire is zero, and the wire can move upward at constant velocity. Part C: To find the magnitude and direction of the minimum magnetic field, write out the forces acting along the y-direction: Forces along y = magnetic force - m*g = 0 (*where m=mass, g=gravity) magnetic force = I*L*B (*where I=current, L=length, B=magnetic field) plugging this into the equation we get: Forces along y = I*L*B - m*g = 0 this can rewritten as : I*L*B = m*g Solving for B, we get: B = (m*g) / I*L*B Part D: The field exceeds the magnitude above, the upward magnetic force exceeds the downward force of gravity, so the wire accelerates upward.