Download Chapter 28 Problem 20 † Given R = 470 Ω C = 10 µF L = 750 mH

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Chapter 28
Problem 20
†
Given
R = 470 Ω
C = 10 µF
L = 750 mH
Vrms = 6.3 V
f = 60 Hz
Solution
Find the rms current for each of the components if they are connected to the power supply.
Resistor
With the resistor attached to the power supply the rms current can be found through Ohm’s law.
Irms =
6.3 V
Vrms
=
R
470 Ω
Irms = 0.0134 A = 13.4 mA
Capacitor
First find the angular frequency.
ω = 2πf = 2π(60 Hz) = 120π rad/s
The capacitive reactance is then
XC =
1
1
=
ωC
(120π rad/s)(10 × 10−6 F )
XC = 265 Ω
Now with the capacitor attached to the power supply the rms current can be found through Ohm’s law
and replacing the resistance with the capacitive reactance.
Irms =
6.3 V
Vrms
=
XC
265 Ω
Irms = 0.0238 A = 23.8 mA
Inductor
The inductive reactance is
XL = ωL = (120π rad/s)(0.75 H)
XL = 283 Ω
Now with the inductor attached to the power supply the rms current can be found through Ohm’s law
and replacing the resistance with the inductive reactance.
Irms =
Vrms
6.3 V
=
XL
283 Ω
Irms = 0.0223 A = 22.3 mA
†
Problem from Essential University Physics, Wolfson