Chapter 5 test

What does it cost per year (at 9 cents per kWH) for ten 150W recessed luminaires to operate if they are turned on to six hours per day?

$300

If the out put is 1,600W and the equipment is 88% efficient, what are the input amperes at 120V?

15 A

In a purely inductive circuit, the CEMF waveform is ______ out of phase with the Applied voltage waveform

180•

The waveform of the CEMF is ____ out of phase with the Applied voltage

180•

What size transformer is required for a 100A, 240V, single phase non continuous load that has a peer factor of 85%?

37.50 kVA

How many 20, 120V circuits are required for forty two 300W incandescent luminaires (noncontinuous load)?

6 circuits

How many 20A, 120V circuits are required for forty two 300W luminaires (non continuous load) that have power factor of 85%?

7 circuits

If you measure voltage and current in an inductive or capacitive and then multiply them together, you obtain the circuits _______

Apparent power

Self induced is 180• degrees out of phase with __________

Applied voltage

The included voltage in a conductor carrying alternating current opposes the change in current flowing through the conductor. The induced voltage that opposes the current flow is called ________

CEMF, counter electromotive force, back-EMF

For ac circuits, the ac _____ of a conductor must be taken into consideration

Eddy currents, skin effects, and resistance

A half wave rectifier can be hard to covert ac voltage into dc voltage to continuously charge a capacitor

False

AC inductive or capacitive reactive loads cause the voltage and current to be in phase with each other

False

Because apparent power is greater then the true power, more loads can be placed on a circuit, and fewer circuits and panels, and smalller transformer might be required

False

The true power of an ac circuit equals the volts times the amperes

False

The total opposition to current flow in ac circuits is called ______ and is measured in ohms

Impedance

In a purely resistive ac circuit, the current and voltage are _________. This means that they both reach their zero and peak value at the same time

In phase

The movement of electrons caused by an external magnetic field is called "_______ current" and the associated potential that is established is called "______ voltage"

Induced

A nonsinusoidal waveform is created when _____ loads distort the voltage and current sine wave

Non linear

In dc circuits, the only property that affects voltage and current flow is

Resistance

As the alternating current through a conductor increases, an expanding and collapsing electromagnetic field through the conductor induces a voltage within the conductor. This is known as "_______ voltage"

Self-induced

The expanding and collapsing magnetic field within the conductor induces a voltage in the conductors CEMF that repels the flowing electrons toward the surface of the conductor

Skin effect

The effective value is equal to the peak value

Times 0.0707 and times 1.41

The peak value is equal to the effective value _________.

Times 1.41

Efficiency describes how much input energy is used for its intended purpose

True

Even when power is removed from the circuit, capacitors can store large amounts of energy for a long period of time. They can discharge and arc if inadvertently shorted or grounded out

True

The magnitude of self induced voltage within a winding is directly proportional to the current flow, the winding, and the frequency at which magnetic fields cut through the winding

True

The movement of electrons themselves does not produce any useful work. It's the effects that the moving electrons have on the loads they flow through that are important

True

When alternating current increases the polarity of CEMF within the conductor tries to prevent from increasing

True

When describing the relationship between voltage and current, the reference waveform is always

Voltage

The opposition offered to the flow of alternating current by a capacitor is called "capacitive reactance" which is expressed in ohms and abbreviated

X C

Self induced voltage opposes the change in current flowing in the conductor. This is called "inductive reactance" and is abbreviated

X L

The abbreviation for impedance is _____

Z