AC/DC practice Test
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102 Terms
What is this symbol?
AC Power Supply
Total voltage in a series circuit can be found
d.All of these
in a parallel circuit total current is equal to :
The average of the individual branch circuit current
When testing a component out of circuit, what setting should you set the DMM to?
Reistance
The DC resistance of a 24VDC heating element is measured with an ohmmeter to be 8.0 ohms. Four 24VDC power supplies are available, each capable of supplying a different amount of current output. Which of the following is the smallest power supply output that can be used to fully power this heating element?
5-amp power supply
In the circuit below, when does the lamp
illuminate?
When the push button is pressed
Given the circuit below, which set of measurements would represent an open filament
in the lamp? The black lead of the meter is connected to the COM port and remains on
point A during all the measurements. The points below would represent the voltage
reading as you moved the red lead throughout the circuit.
B-0V, C-0V, D-12V, E-12V, F-12V
The ammeter in the
circuit below is measuring?
Total current
Given the circuit below, if the 25Ω resistor was open, what would you see if you
measured the total resistance?
it would be infinite (meter reads OL)
Current in a parallel circuit
Is inversely proportional to resistance
Which of the following diagrams contains an open circuit?
A
A step-down transformer is used to change a source's:
voltage
In the circuit below, how could you determine the resistance of the lamp?
Measure it with an ohmmeter
Continuity can be used to check a switch.
True
What standard is used for electrical safety in the workplace?
NFPA 70E
What is the purpose of an input?
All of these
Current in a series circuit?
All of these
A battery is a type of _______ ____________ source.
DC voltage
What is this symbol?
DPST single break switch (contacts)
Circuit breakers and fuses protect against
Both b & c
What is this symbol?
Resistor
What setting would you use on your DMM to find an open in an electrical circuit?
A or C
Which of the following statements is true of reactace in an inductive circuit?
Reactance will increase with increased frequency
If an inductor is in an AC circuit, and the frequency increases,
inductive reactance increases
What is the minimum amount of current to cause a serious injury or even fatality?
.1A
Which of these statements is NOT true about voltage in a parallel circuit with multiple
loads?
Is additive
Calculate the current in the circuit below.
.12
Kirchhoff’s Current Law says that the amount
of current flowing into point A will be the same as the current flowing out of point B.
True
Schematics provide all of the following information except?
Physical location
If there is no service factor listed on a motor nameplate, what should be done?
assume it is 1
Voltage is measured in
Volts
Indicate whether the resistor R2 in the following circuit are in series or parallel?
Parallel
Power is equal to voltage times:
current
A knife switch is an example of a?
Maintained manual switch
Current measurements are taken in
Series
Which of the following is not a correct statement of current and voltage laws
Current flowing into a load will always be greater than the current flowing out of the load since energy is always consumed by a load device.
A capacitor?
Both A & C
Which of these devices is NOT an output?
Relay contacts
A switch that is normally open means?
The contacts remain open until the operator is pressed
What is this symbol?
NO Push Button
In an electrical circuit, power is a measurement of:
work indicated by watts
The type of voltage used in most commercial and industrial buildings is
AC voltage
Which of the following is NOT true about the
circuit below?
The lamp will illuminate in either of the 2 positions of the selector switch
A capacitor stores energy between conduction plates in the form of:
an electrostatic charge
Which of the following statements is true for a parallel circuit?
Each branch in the circuit will have the same voltage
Calculate the main line current in the circuit below.
1.92
Voltage measurements are taken in
Parallel
Inductance is?
Opposition to a change in current flow
A transformer would be needed to:
Power a 120V motor from a 480V power supply
What is this symbol?
DC Power Supply
Which of the following is the total current flow in the circuit shown?
2.0mA
A circuit contains three equal-value resistors in series. Which of the following methods will a tech use to calculate the total resistance?
Add the three values together
Given the circuit below, if the 25Ω resistor was shorted, what would happen to the total
resistance?
it would be reduced
Given the circuit below, if the 75Ω resistor was shorted, how much current would be
flowing in the circuit?
.43A
Resistance is
Opposition to electron flow
What is the first step when measuring resistance?
Turn the power off
Calculate total power used in the circuit below. You must first find total current.
23
What is this symbol?
Magnetic Breaker
Which device uses electromagnetism to create movement?
All of these
Current that is constantly changing direction describes
AC current
In the circuit below, which point has the highest polarity if the negative side of the supply is the common (reference) point?
A
Which of the following is the function of an inductor?
it opposes a change in current flow
What is this symbol?
3 Way Selector Switch
Given the circuit below, which of the following would describe the circuit behavior if R1
was shorted? Assume the power supply is off for all measurements.
all of these
Power is measured in?
Watts
Which of the following describes the characteristics of the two types of electrical current?
Alternating current has a changing voltage level; direct current has a steady voltage level
Calculate total current flow, then determine power used by the circuit below.
1.4
In the circuit below, what is the voltage across the lamp?
12V
Inductors in a DC circuit
Allow current flow
What is this symbol?
Buzzer
Total Power in a series circuit can be found?
Either one of these
Indicate whether the resistor R4 in the following circuit are in series or parallel?
Parallel
According to the NFPA standard for electrical safety in the workplace, which of the following is required to establish an electrically safe work condition?
All of the above
If a capacitor is in an AC circuit, and the frequency increases,
Capacitive reactance decreases
Power is?
The amount of current used in a circuit
Resistance is measured in
Ohms
Resistance measurements are taken in
Parallel
Indicate whether the resistor R1 in the following circuit are in series or parallel?
Series
Current flow in one direction describes
DC current
Capacitors are used for?
Both of these
Total Power in a parallel circuit can be found?
Either one of these
What is this symbol?
DPDT double break switch (contacts)
Given the circuit below, if you suspected the 75Ω resistor was shorted, what steps
would you take to determine this?
turn the power supply off, place your meter in parallel with the 75Ω resistor, set
the meter to ohms, disconnect one side of the resistor, and take the measurement
Voltage was measured at five points (A,B,C,D,E) relative to E in the circuit shown. Which of the following are the two points between which there is a short circuit?
Points C and D
Given the circuit below, which of the following would describe the circuit behavior if R1
was open? Assume the power supply is off for all measurements.
With the ohmmeter across the main line, and R1 disconnected, the meter would
read about 17 Ω
Calculate the total resistance (impedance) in the circuit below.
6.25
Indicate whether the resistor R3 in the following circuit are in series or parallel?
Parallel
Arc flash ratings are based on incident energy levels measured in
Cal/cm2
Inductance is measured in?
Henrys
Which of these statements is NOT true about voltage in a series circuit with multiple
loads?
Is the same throughout the circuit
In the circuit below, calculate the total resistance.
103.1
In the circuit below, the voltage
from point A to point B is 2V. What would the voltage be from point A to point C?
7V
Which of the following is the resistor value of R2 in this circuit?
16 Ohms
Which device creates rotary motion?
Motor
What is this symbol?
Capacitor
What is this symbol?
Thermal Breaker
Current is measured in
Amps
Voltage is ?
The electromotive force that moves electrons
Current is
The flow of electrons
Capacitors are measured in?
Farads