downward 98. A truck drives onto a loop detector and incr component of the magne
ID: 2039242 • Letter: D
Question
downward 98. A truck drives onto a loop detector and incr component of the magnetic field within the loop fro to the larger value B in 0.38 s. The detector is circula of 0.67 m, and consists of three loops of wire. What the induced emf is 8.1 × 10-4 V? detector has a radius A. 3.6 x 10-5 T C. 8.5 × 10-ST B. 7.3 x 10-5 T D. 24 × 10-5 T 99 Suppose a motorcycle increases the downward component of the magnetic field within a loop only from 1.2 x 10-ST to 1.9 x 10-5 T. The detector is square, is 0.75 m on a side, and has four loops of wire. Over what period of time must the magnetic field increase if it is to induce an emf of 1.4 × 10-4 A. 0.028 s C. 0.35 s D. 0.60 sExplanation / Answer
98.
Induced emf is given by:
EMF = N*A*dB/dt
dB = EMF*dt/(N*A)
dB = Bf - Bi
Bf = Bi + EMF*dt/(N*A)
Bf = 1.2*10^-5 + 8.1*10^-4*0.38/(3*pi*0.67^2)
Bf = 8.5*10^-5 T
Correct option is C.
99
from above question
dt = N*A*dB/EMF
dt = 4*0.75*0.75*(1.9 - 1.2)*10^-5/(1.4*10^-4)
dt = 0.1125 sec = 0.11 sec
Correct option is B.
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