4B module 1 test
What's the resistance total of a 10-ohm, a 6-ohm, and a 3-ohm resistor connected in parallel?
1.67 ohms
A self-induced voltage waveform, also known as counter-electromotive force (CEMF), is _____ out-of-phase with the applied voltage waveform.
180
The total resistance of five 14-ohm resistors in parallel is _____ ohms.
2.8
The resistance of a coffee pot is 10 ohms and the resistance of a toaster oven is approximately 6 ohms. What's the total resistance of the two appliances if they're connected in parallel?
3.75 ohms
What's the voltage drop of 125 ft of 12 AWG wire (0.24 ohms) on a balanced 3-wire, 120/240V multiwire circuit supplying a 16A load? (remember round down unless it is a major fraction)
3.80V
A multifamily dwelling (40 units) contains a 4.50 kW electric clothes dryer in each unit. What's the service demand load for all the dryers?
53 kW
What's the voltage drop of 180 ft of 12 AWG wire (0.347 ohms) supplying a 17A load?
6V
A 12-ohm coffee pot is connected in parallel to a 16.09-ohm skillet and wired with a wire having a resistance of 0.07 ohms. What's the total resistance of the loads and the wires of this series-parallel circuit?
7.04 ohms
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.
90
The voltage produced by an ac generator is dependent upon the _____.
All of these
In circuits with _____ loads, the voltage waveform finishes after the current waveform so the voltage "lags" the current.
Capacitive
A waveform is a mathematical representation on a graph that can be used to visualize the level and direction of _____ in a circuit.
Current or voltage
A 115/230V rated dual-voltage motor connected to a 230V circuit must have the motor windings connected in series with each other so each winding will receive 230V.
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.
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.
False
When power supplies are connected in parallel, the voltage of the parallel-connected power supplies and the ampere-hour capacity of the parallel power supplies remain the same.
False
In circuits with _____ loads, the voltage waveform finishes its cycle before the current waveform, so the voltage waveform "leads" the current waveform.
Inductive
A nonsinusoidal (or nonsymmetrical) waveform is produced when multiple alternating-current waveforms of different frequencies are introduced on a circuit, typically by _____.
Nonlinear loads
Series-parallel circuits are less confusing when broken down into a sequence of simple series and parallel problems then solving them by applying _____.
Ohm's Law
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.
Phase
A _____ load has its voltage waveform finishing its cycle at the same time (without lead or lag) as the current waveform.
Resistive
A "lagging" waveform is when the voltage lags behind the current and a "leading" waveform means the voltage leads the current.
True
A pure direct-current waveform displays the polarity and magnitude of the current or voltage as a flat waveform.
True
A series-parallel circuit is one that contains some circuit components connected in series and some components connected in parallel to each other.
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.
True
Circuit wire voltage drop is caused by the resistance of the wires over the length of the path of the circuit as electrons return to the source.
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.
True
Effective current value is also known as the "Root-Mean-Square" (RMS) value.
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
Failure to terminate the phase wires of a multiwire branch circuit to different phases will cause neutral current from the circuits to be additive.
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."
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 the continuity of the neutral wire of a multiwire circuit is interrupted (opened), there could be a fire and/or destruction of electrical equipment resulting from either overvoltage or undervoltage of the circuits.
True
If the current flow through each phase wire of a multiwire circuit is the same, the neutral wire will carry 0A. This applies to 3-wire, 120/240V, single-phase and all three-phase circuits.
True
In a parallel circuit (ignoring voltage drop), the voltage across each resistance is equal to the voltage supplied by the power source.
True
In a parallel circuit, the total circuit resistance is always less than the smallest individual branch's resistance.
True
In a series circuit, the resistance of the circuit (RT) is equal to the sum of the series resistances.
True
One advantage of parallel circuits is that if one branch of a parallel circuit is opened, the power source still provides voltage to the remaining parallel branches.
True
Parallel circuits are used for the electrical wiring of receptacles, lighting, appliances, and equipment.
True
Power factor is a measurement of how far the current waveform is out-of-phase with the voltage waveform.
True
The Formula Wheel is a combination and expansion of the Ohm's Law Formula Circle and Watt's Law.
True
The NEC specifies that the continuity of the neutral wire of a multiwire branch circuit must not be dependent upon any wiring device.
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.
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
True
The power factor of inductive loads causes the VA load to be greater than the true power (watts).
True
The source voltage of a series circuit is equal to the sum of the voltages across all components of the series circuit.
True
The supply voltage of series-connected power supplies is equal to the sum of the voltage ratings of the individual power supplies.
True
The total amount of current flowing through a series circuit is always equal to the current flowing through the individual components of the circuit.
True
The total power consumed in a parallel circuit equals the sum of the powers in each branch.
True
The waveform for alternating-current circuits is symmetrical with positive above and negative below the zero-reference level.
True
There are three methods for calculating the total resistance of a parallel circuit: The Equal Resistance method, the Product-Over-Sum method, and the Reciprocal method.
True
Three-wire, 120/240V, single-phase multiwire branch circuits are more cost effective than two 2-wire, 120V circuits because the 3-wire multiwire circuit has one less wire which permits the use of a smaller raceway.
True
True power is always equal to, or less than, apparent power (VA) and is expressed in watts.
True
Voltage drop can be reduced either by shortening the length of the wire or increasing the wire size to lower the wire's resistance.
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.
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.
True
When describing the relationship between voltage and current waveforms, the reference waveform (the one used to compare against) is the _____.
Voltage
For alternating current, the effective value can be determined by using which of the following formulas?
all of these
In a parallel circuit _____.
all of these
In a series circuit the _____.
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 _____.
all of these
The most significant use of self-induction for industry includes _____.
all of these
The formula used for efficiency calculations is _____.
any of these
When a _____ has reached its maximum potential difference between its metal plates, it's said to be "charged."
capacitor
To discharge a capacitor, a _____ path is required between its positive (+) and negative (
conductive
Kirchhoff's Law tells us that the total _____ of a parallel circuit is equal to the sum of the _____ of all the parallel circuit branches.
current, current
The neutral current returning to the power source of a 3-wire, 120/240V, single-phase circuit is _____ the difference in current flowing through the phase wires.
equal to
Overloading a wire will result in _____ which decreases the service life of the insulating material, and potentially result in a fire from arcing faults.
excessive heat
A wire's resistance is inversely proportional to its length.
false
Capacitance is measured in units of _____.
farads
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.
iron
A(An) _____ branch circuit consists of two or more phase (hot) wires that have a voltage between them and an equal voltage between each phase wire and the neutral wire.
multiwire
A(An) _____ is defined as the wire connected to the neutral point of a power source that's intended to return current from the load back to the power source under normal conditions.
neutral wire
Receptacles connected in parallel result in each receptacle having the same _____.
operating voltage
When working with series-parallel circuits, you need to determine the _____ of the circuit by reducing it down from series to parallel until you have only one _____.
resistance, resistance
Eddy currents are small independent currents near the center of a wire that are a result of _____ from the expanding and collapsing electromagnetic field
self-induction
Current within a series circuit will _____ if any part of the circuit is open.
stop flowing
The neutral current returning to the power source of a 2-wire circuit is _____ the current flowing out of the power source.
the same as
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
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.
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.
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 heating of wires, transformers, and motor windings is wasted energy and is called "power losses."
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.
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
Voltage induced in a wire by its own expanding and collapsing electromagnetic field is known as "self-induced voltage."
true
When alternating current is applied to a capacitor, the current continuously moves back and forth charging and discharging the capacitor.
true
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 _____.
watts
True power is the total energy consumed and is expressed in _____.
watts (P)
When a wire is coiled into adjacent loops (helically wound), it's called a(an) _____.
winding
The total resistance of three 6-ohm resistors in parallel is _____ ohms.
2
Most commercial alternating-current power is produced by a generator driven by _____.
Any of these
"_____" is the ability of a device to store electrical energy and to release that energy.
Capacitance
An electrical circuit where there are two or more paths through which current can flow is called a _____ circuit.
Parallel
_____ circuits aren't used for building wiring, but they are used for equipment control circuits needing to be started or stopped from multiple locations.
Series