Practice PMMI - Industrial Electricity

Given a 208VAC, three phase power source, what is the nominal voltage level from any phase to ground? 0 VAC 104 VAC 120 VAC 208 VAC.

120VAC

What is the voltage output of a transformer supplied with 480 volts operating at a frequency of 50 hertz and a turns ratio of 4:1? 120VAC 1920VAC 240VAC 10VAC

120VAC

What is the total resistance of the circuit shown? 19Ω 27Ω 15Ω 20Ω

15 ohms

How many 1200-watt hair dryers can be operated by a 120V circuit protected by a 20 amp circuit breaker? 0 1 2 3

2

What is the resistance of a circuit that is being supplied by a 100VDC power source that is putting out 5 amps? 500 ohms 20 ohms .05 ohms 25 ohms

20 ohms

What is the total power in the circuit shown? 5 watts 20 watts .4 watts 10 Watts

20 watts. 1st add for total resistance (Rt). 2nd with Rt use ohms law to get current. 3rd use power formula P = I x E to get the final answer 20 watts

Power in a circuit can be determined by Multiplying current by resistance Dividing voltage by current Dividing current by resistance Multiplying current by voltage

Multiplying Current By Voltage

What kind of logic is shown?

NAND

What type of logic is shown in the below diagram?

NOR

What is the total resistance of this circuit? 50Ω 5.5Ω 500 Ω None of these

None

Given the following circuit and information on the next page, which branch contains an open circuit?Ohmmeter reading when all resistors are connected = 438Ω Ohmmeter reading with R1 Disconnected = 448Ω Ohmmeter reading with R2 Disconnected = 530Ω Ohmmeter reading with R3 Disconnected = 780Ω Ohmmeter reading with R4 Disconnected = 690Ω Ohmmeter reading with R5 Disconnected = 438Ω

Ohmmeter reading with R5 Disconnected = 438Ω

The amount a conductor resists the flow of electric current is measured in: Watts Volts Amps Ohms

Ohms

The coil of a relay is a(n): Input Device Output Device Both A and B None of the above

Output

In a 480VAC 3 phase wye system with a neutral, what are the phase to phase and phase to neutral voltages? Phase-Phase = 480VAC, Phase-Neutral = 240VAC Phase-Phase = 480VAC, Phase-Neutral = 277VAC Phase-Phase = 240VAC, Phase-Neutral = 120VAC Phase-Phase = 240VAC, Phase-Neutral = 277VAC

Phase-Phase = 480VAC, Phase-Neutral = 277VAC

Based on the chart and schematic between which two points contain an open? All measurements were referenced to E. Points A to B Points B to C Points C to D Points B to D

Points B to C

The four basic components of an electrical circuit are: Resistance, Reactance, Power, and Conductors Power supply, Outputs, Conductors, and Light bulb Resistance, Power Supply, Inputs, and Outputs Power Supply, Conductors, Outputs, and Inputs.

Power Supply, Conductors, Outputs, and Inputs.

Motors draw FLA when they: Are producing their rated horsepower. Are running under over-loaded conditions. Are running at rated voltage and lightly loaded. None of the above.

Producing their rated horsepower

An AC electric motor has two main parts: the ________ and the ____________. Armature and brushes Stator and slip rings Disconnect switch and fuses Rotor and Stator

Rotor and stator

To measure the voltage drop in a circuit, the voltmeter should be connected in the circuit by: Disconnecting power, removing the wire leading to the device in question, and wiring the meter in its place. Placing the test leads in parallel with the device in question. Removing all but the device in question and measuring the voltage through it. By placing an ammeter in series with the device.

B. Placing the test leads in parallel with the device in question.

Undervoltage protection in a two wire control system Allows the system to 'ride through' voltage sags Ensures the system restarts as soon as the voltage level returns to normal Disables automatic restarts after a power loss Ensures the voltage does not dip below nominal tolerances

Disables the restart button

What is another name for voltage? Electromotive Force Difference in Kinetic Energy between 2 points Current Electromagnetic Field

Electromotive Force

The energy stored in a capacitor is called: Electrostatic charge. Induced voltage. Stored current. Electromagnetic charge.

Electrostatic Charge

All equipment capable of conducting current must be grounded, indicated by Green wire Green wire with yellow stripes Either A or B Neither A nor B

Green Green with yellow stripes

Capacitance is measured in units called: Ohms Henrys Farads Volts

Henry's

Motor slip is defined as An inherent inefficiency within the motor The difference between actual rotor speed and synchronous speed The rotor speed divided by the synchronous speed None of the above

The difference between actual rotor speed and synchronous speed

When a short occurs in one branch of a parallel circuit The other branches will continue to operate It causes an open in the power supply The entire circuit will be shorted None of these

The entire circuit will be shorted

What is the current through the circuit? 300A 3A 1A .33A

.33A

What is the voltage output of a transformers who's turns ratio is 3:1 and has a primary voltage of 240VDC? 80VAC 720VAC 0VAC 120VAC

0VAC

What is the total power of 4 quarter watt resistors wired in Parallel? 1 Watt ¼ Watt 1/16 Watt 4 Watt

1 Watt

What is the total power of 4 quarter watt resistors wired in series? 1 Watt ¼ Watt 1/16 Watt 4 Watt

1 Watt

According to Ohms law what voltage level is required to push 1 amp of current through 1 ohm of resistance? Source voltage 5 volts 1 volt 10 volts

1 volts

If 3, 30ohm resistors are connected in parallel and supplied with 20VDC, what is the total current flow in the circuit? 0.22A .5A 2A 4.5A

2A

How many overloads are needed for a 3-phase induction motor? 1 2 3 4

3

What is the voltage output of a transformers who's turns ratio is 6:1 and has a primary voltage of 240VAC? 60VAC 40VAC 0VAC 1440VAC

40VAC

What is the total power used in a circuit that has ten single phase motors wired in parallel? Each motor pulls 2A at 240VAC with a frequency of 60Hz. 480 Watts 120 Watts 4800 Watts 48 Watts

4800 Watts

A 240VAC source is connected to a 1200 Watt 3-phase motor. How much current is flowing to the motor? 288KA 5A .2A 1.75hp

5A

If a transformer has a VA rating of 1,500, a source voltage of 480VAC and the output voltage is 240VAC, what is the approximate maximum current that can be safely delivered by the transformer? 1 amp 6 amps 10 amps 3 amps

6 amps Power formula. watts / Vs [1500w / 240Vs = 6.25amps]

What is the current flow through R4? 7A 3A 9A 4A

9A

An open in a circuit is: A low resistance path around a load device. A break in the circuit that prevents current flow. A closed switch. A lamp that is illuminated.

A break in the circuit that prevents current flow.

Given three incoming phase conductors A, B and C and a device such as a 3 phase transformer or motor that contains three windings x1-x2, y1-y2, and z1-z2, what would be the proper connections to wire the device to the incoming conductors in a Delta configuration?

A. [A to x1 and z2, B to x2 and y1, C to y2 and z1]

The actual speed of a squirrel cage induction motor is: The synchronous speed. Always the value listed on the name plate. Faster as the motors load increases. Equal to the synchronous speed minus slip.

Always the value on the nameplate

In a typical three-wire AC power cord, which color wire is considered the Hot wire? Red Black White Green

Black

As frequency of an AC source decreases, which of the following statements is true? Capacitive Reactance will increase Inductive Reactance will Increase Capacitive Reactance will decrease Both Inductive Reactance and Capacitive Reactance will decrease.

Capacitive Reactance

The resistance provided by a capacitor in an AC circuit is called: Capacitive reactance. Capacitive resistance Electrostatic resistance. Electromotive reactance.

Capacitive Reactance

What purpose do wire numbers serve? Aid in troubleshooting Connect physical locations of electrical conductors in a panel or circuit to the corresponding electrical point in a print Both A & B None of these

Connect physical locations of electrical conductors in a panel or circuit to the corresponding electrical point in a print

Which device is typically used to control one circuit with contacts in another circuit? Motor Limit Switch Control Relay Push button switch

Control Relay

Which of the following is a form of Ohm's Law? Voltage = Current / Resistance Current = Voltage / Resistance Voltage = Current / Watts Current = Resistance / Voltage

Current = Voltage/Resistance

Which of the following is needed to calculate voltage drop in a conductor? Current, Length of Wire & Cross-sectional area of wire (to calculate Resistance) Power, Length of Wire, Thickness of insulation Power, Thickness of Insulation, Cross-sectional area of the wire None of the above.

Current, Length of Wire & Cross-sectional area of wire (to calculate Resistance)

The purpose of an electrical ladder diagram is to___________________? Depict the physical wiring of the system Depict the physical location of the components in the system Depict the electrical interconnections of the components in the system. All of the above.

Depict Electrical Configurations

Which of the following statements best describes the logic displayed in the shown diagram? If (CR1 and CR2 and CR3) or (CR4 and not CR5) then CR6 If (CR1 or CR2 or CR3) and (CR4 and not CR5) then CR6 If (CR1 or CR4) and (CR2 and CR3) not CR5 then CR6 None of the above.

If (CR1 and CR2 and CR3) or (CR4 and not CR5) then CR6

How should a fuse be installed in a circuit to insure proper operation? On the ground conductor. In series with the Load. In parallel with the load. None of the above.

In series with the load

As frequency of an AC source increases, which of the following statements is true? Capacitive Reactance will increase Inductive Reactance will Increase Inductive Reactance will decrease Both Inductive Reactance and Capacitive Reactance will decrease

Inductive reactance will increase

What is the function of an inductor in a circuit? It opposes changes in voltage. It acts as an open in an AC circuit. It opposes a change in current. It stores energy in an electrostatic field.

It opposes a change in currect

The voltage law that states that the total voltage of a series circuit is equal to the sum of all the voltage drops is Ohm's law. Thevenin's Law Watt's Law Kirchhoff's Law

Kirchhoff's Law

In mutual induction, what passes between conductors in order to create voltage? Radiation Current Magnetic Flux Resistance

Magnetic flux

What is the correct way to measure amperage in a portion of a series or parallel circuit? With the circuit energized, place the meter probes of an ammeter across the component or section of the circuit in question and read the value. Measure the power output of the section of the circuit in question with an ohmmeter and calculate the current using ohms law. Shut off the power to the circuit, open the portion of the circuit in question, wire an ammeter in series, reenergize the circuit and read the value. Measure the voltage output of the power supply and calculate the current using the power equation.

Shut off the power to the circuit, open the portion of the circuit in question, wire an ammeter in series, reenergize the circuit and read the value.

A three-way switch allows the operation of a single load from two different locations. It does this by using what type of switch contacts? Single Pole, Single Throw Double Pole, Single Throw Single Pole, Double Throw Double Pole, Double Throw

Single pole, double throw

In order to reverse the direction of a 3-phase motor, you should Rotate the motor 180 degrees Interlock the forward and reverse contactors Swap T1 and T3 Wire for high voltage

Swap T1 and T3

A battery and a test light can be used to: Test how much inductance is in a circuit. Calculate the resistance of a circuit. Test continuity of a circuit. Prevent a system from losing power.

Test Continuity

A meter is placed on wire 1 and wire 3. PB1 is closed. A reading of source voltage is given. What does this indicate? The circuit is working properly The Stop PB3 is open The Fwd PB1 is open None of these

The Stop PB3 is open. So you are measuring around PB3. If PB3 were closed (in normal state) then you would read zero since PB1 is closed and a path to return exist.

What is true of a capacitor in a DC circuit? The capacitor will charge to the source voltage and then act as an open in the circuit. The capacitor will charge to the source voltage and then act as a short in the circuit. The capacitor will discharge until voltage is removed then act as an open. Capacitors cannot be used in DC circuits.

The capacitor will charge to the source voltage and then act as an open

Conductor ampacity is determined by The cross-sectional area of the conductor How much load is applied to the conductor The heat generated under load, ambient temperature, and the heat resistance of the insulation The nominal voltage required to cause electron flow.

The cross-sectional area of the conductor (Meaning the size or thickness of the wire) Remember the smaller the AWG # of a wire the thicker/larger it is, so the more ampacity it can handle.

Which statement is true for a series circuit? The voltage drop through each component is the same. The total resistance is less than the smallest resistor. The current flow through each component is the same. The power output of each component is the same.

The current flow through each component is the same.

What is the current relationship of the primary and secondary sides of a transformer if the transformer is a 10:1 step-down transformer? The current in the primary and secondary will be the same. The current in the secondary will be approximately 10 times higher than the current in the primary The current in the primary will be approximately 10 times higher than the current in the secondary. Transformers cannot have 10:1 step down ratios.

The current in the secondary will be approximately 10 times higher than the current in the primary.

Which of the following describes inductive reactance? The opposition to changes in voltage The opposition to changes in current The ability for a device to store electrostatic charge The rate at which the chemical reaction in a battery takes place.

The opposition to changes in current

Which statement is true for a parallel circuit? The voltage drop across each component is the same. The total resistance is the sum of all resistors. The current flow through each component is always the same. The power output of each component is the same.

The voltage drop across each component is the same.

The total resistance measure in this circuit is 12 Ohms. What is likely wrong with the circuit? There is an open in R2 There is a short in R1 There is an open in R1 There is a short in R3

There is an open in R1. In a parallel circuit, total resistance should always be less than the smallest resistor value. In this case 12 ohms is less than R2 but greater than R1.

What is the purpose of the NC contact labeled "R" in line 1? To prevent the reverse coil from energizing at the same time as the forward coil To break the seal-in circuit for the forward coil Both A & B None of these

To prevent the reverse coil from energizing at the same time as the forward coil To break the seal-in circuit for the forward coil

The purpose of the neutral wire in a 4-wire system is An alternative to a grounded system To provide a return path to the source To work in conjunction with the safety ground None of the above.

To provide a return path to the source

When is a push-to-test pilot light generally used in circuits? To indicate when a button is pressed To verify the light is working in a critical application To start a machine process To start up an oil pump

To verify the light is working in critical applications

True or False A motor starter contains a coil, contacts, and overloads.

True

True or False Power is equal on both sides of a transformer P = I x E. So if voltage decreases then current will increase proportionately

True

The difference in electrical potential between two points is defined as Current Resistance Voltage Reactance

Voltage

Transformers are used to change a source's: Voltage Frequency Power Resistance.

Voltage

Which method below is the most important way to prevent electrical shock hazards? Only use high quality multimeters Wear insulated rubber gloves Stand on rubber mats Work with circuits and equipment de-energized.

Work with de-energized equipment

Voltage across a set of closed N.O. contacts should be Zero The source voltage Infinite resistance None of the above

Zero

In a 240VAC, 20 amp two wire branch circuit if the maximum allowable voltage drop through the circuit conductors is 2.4VAC, what is the maximum allowable resistance of the circuit conductors?

[.12 ohms] You still use ohms law; but use max allowable voltage 2.4vac and not line voltage 240vac.