In the figure below, a long rectangular conducting loop, of width L, resistance
ID: 1909336 • Letter: I
Question
In the figure below, a long rectangular conducting loop, of width L, resistance R, and mass m is hung in a horizontal, uniform magnetic field that is directed into the page and that exists only above the line aa. The loop is then dropped; during its fall it accelerates until it reaches a certain terminal speed vt. Ignoring air drag, find an expression for vt. (Use any variable or symbol stated above along with the following as necessary: B for the magnetic field strength, and g for the acceleration due to gravity.)
vt =
Explanation / Answer
Fnet =BIL-mg =0
BIL =mg => I =mg/BL
| |=dB/dt
I =||/R
mg/BL =(1/R)(dB/dt) =(1/R)B(dA/dt)
mg/BL =BvtL/R
vt =mgr/(BL)2