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.