4B module 1 test

farads

Capacitance is measured in units of _____.

True

Effective current value is also known as the "Root-Mean-Square" (RMS) value.

Any of these

Most commercial alternating-current power is produced by a generator driven by _____.

True

Power factor is a measurement of how far the current waveform is out-of-phase with the voltage waveform.

watts

Power is the rate at which electrical energy is transferred by an electric circuit in a given amount of time at a steady rate and is measured in _____.

true

Capacitors are also used to store arc producing energy spikes caused by circuit inductance when switch or relay contacts open under load.

true

Capacitors are often used to smooth out pulsating direct-current waveforms when ac is rectified to dc.

any of these

The formula used for efficiency calculations is _____.

watts (P)

True power is the total energy consumed and is expressed in _____.

Capacitance

"_____" is the ability of a device to store electrical energy and to release that energy.

True

A "lagging" waveform is when the voltage lags behind the current and a "leading" waveform means the voltage leads the current.

Resistive

A _____ load has its voltage waveform finishing its cycle at the same time (without lead or lag) as the current waveform.

Nonlinear loads

A nonsinusoidal (or nonsymmetrical) waveform is produced when multiple alternating-current waveforms of different frequencies are introduced on a circuit, typically by _____.

True

A pure direct-current waveform displays the polarity and magnitude of the current or voltage as a flat waveform.

180

A self-induced voltage waveform, also known as counter-electromotive force (CEMF), is _____ out-of-phase with the applied voltage waveform.

False

A simple ac generator can be visualized as a loop of wire rotating within the magnetic lines of force between similar poles of a magnet.

True

A three-phase generator has each of its three windings evenly spaced around the rotor and the windings are 120° out-of-phase from each other.

Current or voltage

A waveform is a mathematical representation on a graph that can be used to visualize the level and direction of _____ in a circuit.

false

A wire's resistance is inversely proportional to its length.

true

Another use for a capacitor is starting single-phase motors. A "start" capacitor is connected to the rotor circuit to create the initial electromagnetic field for the rotor to begin moving.

true

As the frequency at which electromagnetic fields expand and collapse increases, the self-induced voltage within the wire increases.

True

Current flow in an alternating-current circuit moves in both directions due to the changing polarity of the voltage, whereas direct current flows only in one direction.

True

Depending on the instant selected, the instantaneous value can range anywhere from a zero, to a positive peak, or to a negative peak.

self-induction

Eddy currents are small independent currents near the center of a wire that are a result of _____ from the expanding and collapsing electromagnetic field

True

Efficiency describes how much input energy in watts is used for its intended useful purpose and is expressed as a ratio of output power to input power.

True

For a pure resistive load, there's no leading or lagging of the voltage relative to the current. The power factor of the circuit is 100 percent or "Unity."

all of these

For alternating current, the effective value can be determined by using which of the following formulas?

True

For current to flow through a circuit, the power source must apply enough electromotive force (voltage) to cause electrons to flow.

True

Frequency is expressed as cycles per second, or Hertz (Hz).

true

If a capacitor becomes overcharged, the electrons from the negative metal plate can be pulled through the insulation (dielectric) to the positive metal plate by an excessive electric field.

90

In a purely inductive reactive circuit, the self-induced voltage waveform (CEMF) is _____ out-of-phase with the current waveform and 180° out-of-phase with the applied voltage waveform.

Capacitive

In circuits with _____ loads, the voltage waveform finishes after the current waveform so the voltage "lags" the current.

Inductive

In circuits with _____ loads, the voltage waveform finishes its cycle before the current waveform, so the voltage waveform "leads" the current waveform.

true

Root-Mean-Square (RMS) describes the calculation steps (in reverse) necessary to determine the effective ac voltage or ac current value of a waveform.

True

The Formula Wheel is a combination and expansion of the Ohm's Law Formula Circle and Watt's Law.

True

The Power Formula Circle ("Watt's Law") demonstrates the relationship between power, current, and voltage. Watt's Law states that power is equal to current x voltage.

all of these

The _____ the metal plates is(are) factor(s) in determining capacitance.

all of these

The amount of self-induced voltage created within a winding is directly proportional to _____.

True

The effective value of ac voltage or ac current is the equivalent value of dc voltage or dc current that would produce the same amount of heat in a resistor

iron

The electromagnetic field intensity of a coil of wires (winding) carrying alternating current can be increased by inserting a soft _____ core within the wire winding.

true

The heating of wires, transformers, and motor windings is wasted energy and is called "power losses."

all of these

The most significant use of self-induction for industry includes _____.

true

The only thing needed to induce voltage is relative motion between a wire and an electromagnetic field and is the principle that explains how generators and transformers function.

False

The peak value of a waveform is the maximum value the current or voltage waveform reaches during each full cycle of the rotation of the generator's rotor.

True

The power factor of inductive loads causes the VA load to be greater than the true power (watts).

true

The resistance in a wire is inversely proportional to its cross-sectional area. If the wire's diameter is increased, then its resistance will decrease.

True

The total power consumed in a parallel circuit equals the sum of the powers in each branch.

All of these

The voltage produced by an ac generator is dependent upon the _____.

True

The waveform for alternating-current circuits is symmetrical with positive above and negative below the zero-reference level.

conductive

To discharge a capacitor, a _____ path is required between its positive (+) and negative (

True

True power is always equal to, or less than, apparent power (VA) and is expressed in watts.

true

Voltage induced in a wire by its own expanding and collapsing electromagnetic field is known as "self-induced voltage."

True

Waveforms that are "in-phase" with each other means that at every instant, the current is exactly in step with the applied voltage, and both the current and voltage waveforms reach their zero and peak values at the same instant in time.

capacitor

When a _____ has reached its maximum potential difference between its metal plates, it's said to be "charged."

True

When a magnetic field moves through a coil of wire, the lines of force of the magnetic field cause electrons in the wire to flow in a specific direction. When the magnetic field moves in the opposite direction, electrons in the wire flow in the opposite direction.

winding

When a wire is coiled into adjacent loops (helically wound), it's called a(an) _____.

true

When alternating current is applied to a capacitor, the current continuously moves back and forth charging and discharging the capacitor.

Voltage

When describing the relationship between voltage and current waveforms, the reference waveform (the one used to compare against) is the _____.

Phase

When the term "_____" is used in relation to waveforms, it indicates the degree relationship between two waveforms, such as voltage-to-current or voltage-to-voltage.