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PhysicsEMI/ACMotional & Rotational EMFHard2 minPYQ_2016
PhysicsHardmultiple choice

A rigid wire loop of square shape having side of length L and resistance R is moving along the x-axis with a constant velocity v0 in the plane of the paper. At t = 0, the right edge of the loop enters a region of length 3L where there is a uniform magnetic field B0 into the plane of the paper, as shown in the figure. For sufficiently large v0, the loop eventually crosses the region. Let x be the location of the right edge of the loop. Let v(x), I(x) and F(x) represent the velocity of the loop, current in the loop, and force on the loop, respectively, as a function of x. Counter-clockwise current is taken as positive.

Which of the following schematic plot(s) is(are) correct ? (Ignore gravity)

Question diagram: A rigid wire loop of square shape having side of length L an

Options:(select one or more)

Answer:
C, D
Solution:


When loop was entering (x < L)
ϕ=BLx
e=dϕdt=-BLdxdt
e=BLV
i=eR=BLVRACW
F=iB(Left direction) =B2L2VR(in left direction)
   a=Fm=B2L2VmR    a=VdVdx
VdVdx=B2L2VmR     V0VdV= -B2L2mR 0xdx
   V=V0-B2L2mRx(straight line of negative slope for x < L)
I=BLR V  (I vs x will also be straight line of negative slope for x < L)
Lx3L

dϕdt=0
e=0  i=0
F = 0
x>4L

e=Blv
Force also will be in left direction.
i=BLWR(clockwise)a=B2L2VmR=VdVdx
F=B2L2VR Lx-B2L2mRdx=ViVfdV
  B2L2mRx-L=Vf-Vi
Vf=Vi-B2L2mRx-L(straight line of negative slope)
I=BLVR(Clockwise) (straight line of negative slope)

Stream:JEE_ADVSubject:PhysicsTopic:EMI/ACSubtopic:Motional & Rotational EMF
2mℹ️ Source: PYQ_2016

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