Wiring Circuits 1 Final

Is it true that a low-voltage system cannot harm you?

No. A low-voltage system CAN harm you.

What tool is properly grounded?

A tool with a 3-prong plug connected to a 3-prong receptacle

Describe what a GFCI does, and what environment it is used in.

A GFCI is commonly used in wet or moist environments. They are used to monitor electrical current flowing through a circuit. They compare the current entering the circuit with the current returning. If the difference is more than 5 ma, the device shuts down. They compare the current on both legs of the circuit

What are the four steps to take when testing a circuit for voltage?

1. Ensure circuit is off

2. Test Multimeter on a known voltage souce

3. Test the circuit

4. Retest the multimeter

What is a major difference between a circuit breaker and a fuse?

Circuit breakers can be reset. Fuses can only be used once

What electrical wire size is larger in diameter, AWG 14 or AWG 12

In the AWG system, the smaller the gauge number, the larger the diameter of the wire. So AWG 12 is larger

Why is consideration of electrical wire size important when wiring an electrical circuit?

1. Smaller wires can overheat

2. Efficiency

Explain the Arc Thermal Performance Rating for flame-resistant clothing.

1. indicates the level of protection the clothing provides for burns from electric arcs

2. Expressed in calories per square centimeter

3. Related to the probability of receiving a second-degree burn

What unit is current of electric flow measured in?

Amperes/Amps

To avoid electrical​ shock, technicians​ should do what?

Make sure that the unit is grounded, and make sure he himself is not grounded.

Power tools that are properly grounded​ require:

A two-prong electrical plug.

What is the difference between static electricity and dynamic electricity?

Static Electricity: buildup of electrical charge on a surface

Dynamic: Occurs when other forms of energy are converted into electrical energy, such as chemical.

Which formula is used to calculate​ watts?

Volts x Amps= Watts

The frequency of the waves in alternating current is measured in​ __________.

Hertz

• Explain the relationship between current and resistance in an electrical circuit

Current and resistance are inversely related

• What is meant by the frequency of AC current?

the number of cycles a current completes in one second. It is measured in Hertz

What is Ohm’s Law?

A principle in electronics that relates voltage, current, and resistance in an electrical circuit

It is expressed by this formula: E= I x R

E=voltage in volts

I - the current in amps

R- the resistance in Ohms

Which of the following is a good example of an​ insulator?

Ceramic

What are the different formulas for Ohms law?

1. I (current) = E (voltage)/ R (resistance)

2. R (resistance)= E/I(current)

What is the formula used to calculate electric power?

P (power)= I x E

What is the formula for calculating current draw when you are given the wattage of an object?

I = P (power, in wattage) / E (voltage)

Generators use which two types of energy to create​ electricity?

Mechanical and magnetic energy.

A circuit that has only one path for the current to flow is called a​ __________ circuit.

Series circuit

In a parallel​ circuit, the voltage stays the same. True or False?

True

What happens to current if voltage remains the same and resistance goes​ up?

Current will go down

If resistance remains the​ same, what will happen to voltage if current goes​ down?

Voltage goes down

How do you find total resistance in a series circuit?

Total resistance is the sum of all of the individual resistances

A series circuit of three resistors of​ 4, 5, and 6 ohms each has a current of 2 amps. What voltage is there across the 5 ohm​ resistor?

Formula: current x ohms

so you would do 2 × 5 ohms to get the voltage across the 5 ohms resistor.

Answer: 10 volts

What is the formula for parallel circuit current?

I=E/R

Which statement about series and parallel circuits is​ TRUE?

In a series and parallel circuit, the voltage stays the same

How do you find total resistance of multiple resistors in a parallel circuit?

Take the resistance (15 ohms for example) and divide it by the number of resistors.

What is the formula for voltage if amps and watts are known?

E=P/I

The three general types of materials used in electrical control systems​ are:

conductors, semiconductors, and nonconductors

Before handling printed circuit​ boards, technicians should discharge any static electricity from their bodies​ by:

Touching a grounded metal frame.

The electromotive force that causes electrons to move along a conductor is​ called what?

Voltage

Electrical potential is measured​ in:

Volts.

Electrical potential​ is:

The ability to make current flow.

In an electrical​ circuit, amps​ are:

1 coulomb of electrons flowing in 1 second

The number of cyclic wave forms present at one time in an AC circuit is​ called:

A phase.

Alternating current is typically available​ in:

Single-phase and three-phase.

An electric circuit that contains a source and path without a load is​ called:

A short-circuit

An electric circuit without a complete path is​ called:

An open-circuit.

In refrigeration and air​ conditioning, switches are normally​ wired:

In series with the load they control.

In refrigeration and air​ conditioning, safety controls are​ wired:

In series with the load they protect.

In refrigeration and air​ conditioning, loads are normally​ wired:

In parallel with eachother.

The voltage in a series​ circuit:

Drops across each load.

The current in a parallel​ circuit:

increases as more loads are added.

The total circuit resistance of a parallel circuit will always​ be:

Less than the lowest individual resistance

In a basic electric circuit with a steady​ potential, when resistance​ decreases:

Current increases.

In a basic electric circuit with a fixed​ resistance, when voltage​ increases:

Current increases

The power company supplies residential users with how much power over the incoming​ lines?

240 Volts.

In a solenoid​ valve, which part of the valve acts to provide a path for the flux for the magnetic​ field?

The plunger

AC power can be converted to DC power through use of components​ called:

Rectifiers

A transformer uses this electrical principle to increase or reduce voltage with no moving parts or contacts.

Induction

In an AC inductive​ circuit:

Voltage leads current

In an AC resistive​ circuit:

The voltage and current are in phase.

What is the purpose of a capacitor in an AC motor​ circuit?

It provides a phase shift so the motor can start more easily.

In an AC capacitive​ circuit:

Current leads voltage

What is the formula for calculating impedance?

Z (impedance)= E(volts)/I (Current)

Why​ can't impedances in series in an AC circuit simply be added to find the total circuit​ impedance?

Because the currents are out of phase with eachother

Impedance is the combined effect​ of:

Resistance, and inductive and capacitive reactance

​Three-phase AC power is​ used:

Only in commercial buildings

The voltage between the​ "stinger" leg of a delta transformer and ground​ is:

208 V

​Three-phase transformers are available​ in:

Delta and Wye configurations

A delta​ three-phase power supply​ provides:

240 V between the legs

A wye​ three-phase power supply​ provides:

208 V between the legs.

The voltage between any leg of a 480 V wye transformer and ground​ is:

277 V

​Single-phase AC power is​ used:

In both residential and commercial buildings

How often do you retest insulated rubber gloves?

Every 6 months

What is a characteristic of a residential service​ panel?

The panel has a neutral grounded connector

The safest category of electric meters​ is:

Category IV

Category II electric meters are safe for working on which types of​ circuits?

circuits inside an appliance that plug into a 120 volt receptacle

How can a noncontact voltage detector be used to indicate a tripped​ breaker?

The detector will not show voltage leaving the breaker

What is the best tool for determining if an electrical wire running through a space where you are working is​ energized?

A noncontact voltage detector.

What is the advantage of a noncontact voltage detector over a​ voltmeter?

It doesn’t have to touch the energized circuit

The lower the AWG number for a wire, the higher the:

Current that it can carry

The American Wire Gauge rates wires in size from smallest to largest​ as:

50 to 0000

What gauge wire is most often used for residential receptacle​ circuits?

12 Gauge

When replacing a fuse you must match​ the:

Volt, amp, instantaneous current, and physical size

Which of the following describes a​ dual-element fuse?

It provides a time delay for starting motor loads

What is the instantaneous rating of a​ fuse?

A rating of the maximum current that the fuse can safely interrupt

Which 2 categories can be divided into?

Line voltage and low-voltage.

What is the formula for calculating secondary voltage winding on transformer?

Vs(secondary voltage)/Vp (primary)=Ns(# of secondary windings)/Np (# of primary windings)

It is expressed as a ratio

The purpose of a standard control transformer is​ to:

Reduce line voltage to 24V for HVACR control systems

Heat pump thermostats generally require two stages of heating in order to​ control:

The auxiliary heat.

How does a remote bulb thermostat​ work?

Pressure in the bulb rises and falls with temperature

Line voltage thermostats can usually​ switch:

15 Amps

What is the formula to find safe secondary current?

Secondary current= VA/ secondary voltage

Which type of thermostats provide the closest temperature​ control?

Electronic low-voltage thermostats

What is the most common form of switching used for mechanical​ thermostats?

Mercury bulb

What is used as the sensing element in a mechanical​ humidistat?

A nylon ribbon or hair

Two common​ pressure-sensing devices used in pressure controls​ are:

bellows and diaphragm

What is cut out differential?

If you want to set your cut-out at a certain value, it will be the cut-in psig - the differetntial

A solenoid coil is a​ doughnut-shaped coil of wire that​ produce:

A magnetic field

The movement of a​ solenoid's plunger can be used to control many HVACR electrical devices​ including:

Thermostats

When do normally open relay contacts​ close?

When the relay coil is energized

What device can best be described as an electrically operated​ switch?

a relay

Electrical symbols in ladder and schematic​ diagrams:

Represent electrical properties of common components

Electrical symbols in ladder and schematic diagrams represent:

Electrical properties of common components