l T-Mobile * 1096( -+ 11:13 PM mail.shsu.edu 9.0 V 5.5 ? 8. A solenoid with a cr
ID: 2039675 • Letter: L
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l T-Mobile * 1096( -+ 11:13 PM mail.shsu.edu 9.0 V 5.5 ? 8. A solenoid with a cross-sectional area of 1.75x10-3 m2 is 0.780 m long and has 450 turns per meter. Find the magnitude of induced emf in this solenoid if the current in it is increased from 0 to 1.65 A in 50.5 milliseconds. 9. An ac generator with a frequency of 1.34 kHz and an rms voltage of 23.2V is connected in series with a 2.20kO resistor and a 310 mH inductor. What is the power factor for this circuit? What is the average power consumed by this circuit? 10. 11. A 55-kW radio station broadcasts its signal uniformly in all directions. What is the average intensity of its signal at a distance of 250 m from the antenna? 12. A television is tuned to a station broadcasting at a frequency of 6.60x 107 Hz . For best reception, the rabbit-ear antenna used by the TV should be adjusted to have a tip-to-tip length equal to half a wavelength of the broadcast signal. Find the optimum length of the antenna.Explanation / Answer
8) self inductance of the solneoid, L = mue*n^2*A*l
= 4*pi*10^-7*450^2*1.75*10^-3*0.78
= 3.47*10^-4 H
induced emf = L*dI/dt
= 3.47*10^-4*(1.65 - 0)/(50.5*10^-3)
= 0.0113 V
9)
inductive reactnace, XL = 2*pi*f*L
= 2*pi*1.34*10^3*310*10^-3
= 2610 ohms
imepdance of the ckt, z = sqrt(R^2 + XL^2)
= sqrt(2200^2 + 2610^2)
= 3413 ohms
power factor, cos(phi) = R/z
= 2200/3413
= 0.644 <<<<<<<<-----Answer
Irms = Vrms/z
= 23.2/3413
= 0.0068 A
Average power consumed, Pavg = Irms^2*R
= 0.0068^2*2200
= 0.102 W
11) Intensity = power/Area
= 55*10^3/(4*pi*250^2)
= 0.0700 W/m^2
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