AC Theory Final Study Guide

What is the Total current formula?

IT √ IR^2 + IL^2

What is the impedance of the parallel RL Branch in the Figure below? Given: R1 = 75 ohms R2 75ohms XL= 75 ohms

** assume voltage at 75** Z =√ (R^2+ XL)^2 Z =√ (75^2 + 75)^2 = 106.06 divide by 2 because of 2 circuits = 53.03 at 45 degrees Total impedance = 53.03

What is the Frequency resonance formula?

1 / 2π√ H x F

What is the True Power formula with PF

ET x IT x PF = True Power

What is the Eapp Formula?

Eapp = IT x Z

What is the total current for the circuit in the figure below? Given: ET = 38 V XC 75 ohms XL = 1000 ohms

XC x XL / XC - XL 75 x 1000 / 75 - 1000 Z = 81.08 E = I x R 38 = I x 81.08 I = .4687 amps

What is the power factor for the circuit for in the figure below? Given: R =250 ohms L = 750 mH

XL = 2πfL = 2 x π x 60 x 750 XL= 282.74 Z = √ R^2 + XL^2 =√250^2+ 282.74^2 Z= 377.41 PF = A / H x 100 PF = R / Z x 100 =250 / 377.41 x 100 = 66.24 PF = 66.24

What is the Impedance total formula

XT = XL x XC / XC +(-XL)

what is the total current for the circuit in the figure below? Given: R = 60 ohms XL = 150 ohms a. 1.14 amps b. 2.8 amps c. 3.7 amps d. 5.3 amps

b. 2.8 amps Fr = XC = XL R = 120 / 60 = 2 amps XL = 120 / 150 = .8 amps

What is the capacitive reactance of a circuit with 80 ohms of inductive reactance at resonant frequency? a. 35 ohms b. 80 ohms c. 240 ohms d. 277 ohms

b. 80 ohms FR = XL = XC

If a series LC circuit has an XL = 50 ohms, an XC = 50 ohms, and the frequency is decreased from 400 to 250 Hz the circuit will become ________? a. conductive b. capacitive c. resistive d. inductive

b. capacitive XL goes down = XC goes up capacitive XL goes down = 2πfL frequency goes down = inductive XL goes up = 1/2πfL frequency goes down = capacitive

If the frequency is increased in a series RL circuit, the power factor will ______? a. increase b. decrease c. remain the same d. vanish

b. decrease XL^ = 2π(f^)L if the XL goes up the frequency goes up PF goes down = R / Z the impedance goes up Z^ = √ R^2 +(XT^2)^^^ If the impedance goes up then the XT goes up

If the frequency is increased in a series RC circuit, the power factor will ________. a. vanish b. increase c. remain the same d. decrease

b. increase ^XC = 1/2π(f)c If the XC goes down the frequency goes up (Z) = √R^2 + (XT^2) If the impedance Z goes down then the XT goes down PF^ = (R / Z)x 100 If the Power factor goes up the R / Z goes down

What is the total capacitance for the circuit in the figure below? Given: R1 = 400 ohms R2 = 125 ohms C1 = 3 uF C2 = 15 uF a. 2 uF b. 3.7 uF c. 18 uF d. 45 uF

c. 18 uF C1 + C2 ... C3 = CT

Inductive reactance and capacitive reactance oppose each other by _________ degrees? a. 0 b. 90 c. 180 d. 270

c. 180 degrees XL goes up.. Resistance goes horizontal and XC goes down

A circuit is considered to be resonant when ________. a. frequency is at a minimum b. frequency is at maximum c. XL equals XC d. all currents are in phase

c. XL equals XC

The ________ will be the same through all parts of a series RC circuit. a. voltage b. reactance c. current d. impedance

c. current Z = ET / IT

What is the total current for the circuit in the figure below? Given: Z = 275 ohms ET = 38V Xc = 75 ohms XL = 1000 ohms a. 57 mA b. 61 mA c. 96 mA d. 138 mA

d. 138 mA IT = ET / Z = 38/ 275 = .138

What is the resonant frequency for the circuit with a 0.24 uF capacitor and a 56 microhenry inductor in parallel. a. 3.14 kHz b. 11.2 kHz c. 22.5 kHz d. 43.4 kHz

d. 43.4 kHz 1/ 2π√ H x Farads (6.28 √(( Hx 10^-6)x(Cx10^-6))^-1

If the frequency is increased in a series RL circuit the phase angle will ________. a. remain the same b. vanish c. decrease d. increase

d. increase

What is the impedance of a series circuit with 150 ohms of resistance and 325 ohms of reactance. a. 103 ohms b. 175 ohms c. 475 ohms d. none of these

d. none of these Z = √ R^2 + (XT^2)

What is the Power factor formula

PF = R / Z x 100

What is the impedance formula?

Z = √ R^2 + (XL- XC)^2

What is the True Power Formula?

IT^2 x R = True Power

What is the true power for a circuit with an applied voltage of 277 volts, a current draw of 16 amps and a power factor of 86 percent? a. 3.81 kW b. 4.42 KW c. 5.34 kw d. 7.62 kw

PF = TP / AP AP = 277 volts x 16 amps = 4432 .86 = TP / 4432 4432 x .86 = TP / 4432 x 4432 3811.52 = TP convert it to KW a. 3.81 KW

What would the impedance for the circuit in the figure below if the total current flow was 6 amps?

Z = ET / IT = 120 / 6 = 20 impedance

What is the current formula when XC and XL are included

Z = R x XL / R^2 x XL^2 E = I x R

What is the impedance of the circuit in the figure below? Given: R = 750 ohms XL = 250 ohms XC = 100 ohms

Z = √ R ^2 + ( XL - XC) ^2 =√ 750^2 + (250-100)^2 Z =764.85 ohms

***What is the true power in the circuit in the figure below? Given: R = 55 ohms XL = 250 ohms Xc = 400 ohms ET = 120V

Z = √ R ^2 + ( XL - XC) ^2 Z = √ 55 ^2 + (250-400) ^2 Z = 159.77 ohms E = I x R 120 = I x 159.77 120 / 159.77 = I 0.75 amps = I P = I^2 x R = .75^2 x 55 = 30.937 round up = 31.03 Watts

What is the applied voltage for the circuit in the figure below? Given XL = 80 ohms and XC = 32 ohms

Z =√ R ^2 + (XL-XC)^2 =0+ (80-32) (get rid of the 2nd power because of Sq. root) = 48 ET = IT x Z = 48 x 7 amps ET =336 volts

What is the current flow around the capacitor of the circuit in the figure below? Given: IT = 6 A Zrc = 125 ohms XC = 50 ohms R2 50 ohms R1 50 ohms

Z rc = 125 ohms E = I x R E = 6 x 125 750 V I = E / R 750 / 50 = 15 amps