AC Theory Level 2 Third Edition Lesson 4: Understanding and working with parallel RL Circuits

The circuit shown contains two resistors and two inductors, all connected in parallel.

TRUE

A resistor and an inductor are connected in parallel. If the voltage across the resistor is 120 volts, the voltage across the inductor is 120 volts.

TRUE

A resistor and an inductor are connected in parallel. What is the phase relationship between the two voltages?

A

In a series RL circuit, the ? are in-phase, and the ? are out-of-phase. In a parallel RL circuit, the ? are in-phase, and the ? are out-of-phase.

B

Two resistors are connected in parallel. One has a current flow of 2 amperes and the other draws 4 amperes. What is the total current?

6A

A resistor and an inductor are connected in parallel. The resistor draws 2 amperes and the inductance 4 amperes. The total current is 6 amperes.

FALSE

The current through the resistive branch of a parallel circuit is ? out-of-phase with the current through the inductive branch.

D

In a parallel circuit, IR and IL must be added vectorially to find the total current.

Select one:

TRUE

When analyzing the current in a parallel RL circuit with a large R and a small value of XL, the phase angle theta is close to 0°.

FALSE

Given the circuit and parameters shown, solve for the following: (Round the FINAL answers to whole numbers unless otherwise noted.)

4A

3A

5A

24OHMS

80%

36.8 Degrees

The current vector diagram represents the values of IR, IL, IT, and angle theta for the circuit shown. Place each label and value in the appropriate locations. (Be sure to place variables to the left and values to the right of the equals sign.)

On Top:

IR=4A

Bottom Left: IL=3A

BottomRight: IT=5A

The impedance of a parallel RL circuit is always less than the resistance or reactance of any one branch.

TRUE

In a parallel RL circuit, the ? can be computed by multiplying the line voltage by the line current.

A

The power factor in a parallel RL circuit is the ratio of ? to ? .

D

A circuit has an applied voltage of 240 volts and draws 5 amperes. The power factor is 70%. What is the apparent power? The values calculated for this question will be used for additional questions.

1200VA

A circuit has an applied voltage of 240 volts and draws 5 amperes. The power factor is 70%. What is the true power?

840W

Complete the following statements regarding a parallel RL circuit where the frequency is increased.

INCREASE

INCREASE

DECREASE

DECREASE

INCREASE

In a series RL circuit, the vector sum of the currents equals the total current.

FALSE

In a series RL circuit, power delivered by the source is apparent power.

TRUE

In a parallel RL circuit, power delivered by the source is apparent power.

TRUE

When the resistance of a parallel RL circuit is increased, the circuit becomes more inductive.

TRUE

When the resistance of a series RL circuit is increased, the circuit becomes more inductive.

FALSE

When the inductance of a series RL circuit increases, θ increases.

TRUE

In a parallel RL circuit, the voltage across each branch is the same.

TRUE

The current is the same at all points in a parallel RL circuit.

FALSE

Using this formula: , solve for Z in the circuit shown. (Round the FINAL answer to two decimal places.)

233.32OHMS

Solve for the impedance of the circuit shown by determining branch currents and total current using Ohm's Law. (Round the FINAL answer to two decimal places.)

233.32 OHMS