AC Theory, Lvl II - Lesson 1: Comprehending the Parameters of Series RL Circuits

Which of the following figures shows an inductor and resistor in series with an AC source?

*The picture with a coil and a resistor in series. If your not sure about the symbols then google what they look like. I'm not paying for plus just to show some pictures.

When R and XL are present in a circuit, theta is somewhere between ? and ? .

0° / 90°

1. The voltage drop across a resistor in a circuit can be determined by the formula ? 2. The Voltage drop across an inductor in a circuit can be determined by the formula ?

1. ER = IR x R 2. EL = IL x XL

In this series circuit, the voltage drop across the resistor is 130 volts, and the applied voltage is 150 volts. What is the voltage drop across the coil? (Round the FINAL answer to one decimal place.)

74.8V

A 480-volt circuit has an impedance of 60 ohms. What is the current?

8 A

VARs represents the product of the volts and amps that are ? out-of-phase with each other.

90 degrees

In a circuit containing only inductance (if this is possible), what is the phase relationship between the current and the applied voltage?

90 degrees out-of-phase, lagging.

Drag the terms below to the appropriate locations to properly label the voltage vectors for the circuit shown. (Be sure to place variables to the left and values to the right of the equals sign.)

Arrow pointing up (signifying the opposite side a right triangle) - EL = 74.8V Arrow crossing diagonally (signifying the hypotenuse of a right triangle) - ET = 150V Arrow crossing horizontally (signifying the adjacent side of a right triangle) - ER = 130V

One of the primary laws for series circuits is that the ? must be the same in any part of the circuit.

Current

Coils do not have resistance.

False

Inductive reactance of a circuit is directly proportional to ? . I. current II. frequency III. inductance IV. resistance V. voltage

II and III

Solve for the total current, power factor, and phase angle for the circuit shown. (Round the FINAL answers to at least two decimal places in the specified unit.)

IT = 29.58mA Power Factor = 36.97% Angle θ = 68.3 degrees

Solve for the total current in the circuit shown, first at 1,000 hertz and then at 2,000 hertz. (Round the FINAL answers to at least two decimal places in the specified unit.)

IT@1000Hz = 7.31mA IT@2000Hz = 4.21mA

Both resistance and inductive reactance oppose current flow, and their combined opposition is called ? .

Impedance

Refer to the formula XL = 2πfL. If L increases, XL ? , and if f increases, XL ? .

Increases/Increases

Which is the correct formula for determining total inductance in a circuit containing three inductors in series?

LT = L1 + L2 + L3

Inductive reactance is measured in ? and is designated by ? . Impedance is measured in ? and is designated by ? . Resistance is measured in ? and is designated by ? .

Ohms/XL Ohms/Z Ohms/R

If a circuit contains ? , the current and the applied voltage will always be in-phase.

Only resistance

Drag the variables below to the appropriate locations to create the equation to determine power factor.

PF = Ptrue/Papp x 100

Power factor is generally expressed as a(n) ? .

Percentage

The ratio of a coil's inductive reactance to resistance is referred to as the coil's ? whose symbol is ? .

Quality Factor/Q

Which is the correct formula for determining total resistance in a circuit containing three resistors in series?

RT = R1 + R2 + R3

The angular displacement by which the voltage and current are out-of-phase with each other is referred to as ? .

The angle theta

What is meant by the statement that the circuit is a RL circuit?

The circuit contains inductive reactance and resistance

Determine how the following circuit characteristics will be affected if the frequency is increased in a series AC circuit containing a resistor and an inductor. The current will ? = The inductive reactance will ? = The voltage drop across the resistor will ? = The voltage drop across the inductor will ? = The phase angle will ? = The power factor will ? = The resistance will ? = The applied voltage will ? = The true power will ? =

The impedance will ? = Increase The current will ? = Decrease The inductive reactance will ? = Increase The voltage drop across the resistor will ? = Decrease The voltage drop across the inductor will ? = Increase The phase angle will ? = Increase The power factor will ? = Decrease The resistance will ? = Remain the same The applied voltage will ? = Remain the same The true power will ? = Decrease

To find the total impedance for a series RL circuit, vector addition must be used.

True

Using the impedance triangle is just one method of graphically showing how out-of-phase quantities can be added.

True

The power factor (PF) is a ratio of the ? power to ? power.

True/Apparent

? is the equation for finding inductive reactance

XL = 2πfL

Solve for the impedance, and then angle theta for the circuit shown. (Round the FINAL answers to at least two decimal places in the specified unit.)

Z = 144.22 ohms Angle θ = 33.69 degrees

The ? of the angle theta (∠θ) in a power triangle is also the power factor.

cosine

1. Which is the correct formula for determining total resistance in a circuit containing three resistors in parallel?

d. RT = 1/ 1/R1 + 1/R2 + 1/R3

More resistance in a RL series circuit causes the vertical component of an impedance triangle to become relatively ? with a ? phase angle.

shorter/smaller